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Bulletin of the Museum of Comparative Zoology 
AT HARVARD COLLEGE. 
Wotne se KOMeV ED. NOL -E: 


AN ATLANTIC “PALOLO,” STAUROCEPHALUS 
GREGARICUS. 


By ALFRED GOLDSBOROUGH MAYER. 


Witn THREE PLATES. 


CAMBRIDGE, MASS., U.S. A. : 


PRINTED FOR THE MUSEUM. 
June, 1900. 


JUN 12 1900 


No. 1.— An Atlantic “ Palolo,” Staurocephalus gregaricus. 
By ALFRED GOLDSBOROUGH MAYER. 


Durine the summers of 1898 and 1899 I was acting as assistant to 
Dr. Alexander Agassiz in making a study of Medusz at Loggerhead 
Key, one of the Tortugas Islands, Florida; and it was while thus en- 
gaged that the remarkable breeding habits of the worm about to be 
described were observed. 

It gives me pleasure to express my appreciation of the generous kind- 
ness of Dr. Agassiz, to whose permission I owe the privilege of publish- 
ing this paper. 

It is also a pleasure to remember the constant interest and kindness 
of George R. Billbury, Esq., head keeper of the lighthouse at Loggerhead 
Key, who did everything in his power to further the scientific work, and 
to render my stay at the Tortugas enjoyable. 

I also wish to thank Major J. E. Sawyer, U. S. A., who kindly 
allowed the use of the government steamer, ‘“ George W. Childs,” in 
transporting me and my apparatus to and fro from Key West to the 
Dry Tortugas. 

The worm about to be described in this paper appears to possess 
breeding habits so closely similar to those of the well-known Palolo 
worm ? of the South Pacific that I am inspired to give to it the title of 
the Atlantic “Palolo.” Our Atlantic ‘ Palolo,’’ however, is a new 
species of the genus Staurocephalus, and is therefore quite distinct 
from the Palolo or Bololo worm (Palolo viridis, Gray ; Lysidice viridis, 
Collin) of Samoa and Fiji, that swarms in vast numbers, for breeding 
purposes, upon the surface of the ocean, early in the morning of the 
days of the last quarter of the October and November moons. 


1 Tt is not the purpose of this paper to discuss the habits of the Pacific Palolo. 
Good scientific accounts of its wonderful swarming habit may be obtained from 
the writings of S. J. Whitmee, 1875; W. C. McIntosh, 1885; A. Collin, 1897; 
B. Friedlander, 1898; and A. Agassiz, 1898. See “ Bibliography” at the end of 
this paper. 

VOL. XXXVI.— NO. I. 1 


2 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


We will first present an account of the swarming of the Atlantic 
Palolo, and will then give a description of the adult worm, a history of 
the development of its larva, and finally some general conclusions con- 
cerning the breeding habits of Polychete. 

It seems probable that the time of the swarming of the Atlantic 
Palolo is directly related to the date of the last quarter of the moon, 
for in 1898 the swarm occurred on July 9, and the last quarter of the 
moon on July 10; while in 1899 the worm swarmed on July 1, and the 
last quarter of the moon fell on June 29. In 1898 about two hundred 
specimens of the worm were seen to swarm on the morning of July 8, 
but on the following day the animals appeared in vast numbers, while 
on July 10 only about a dozen specimens could be found after a careful 
search. In 1899 a wonderfully dense swarm appeared suddenly on the 
morning of July 1, and only a few worms were to be seen on July 2, 
after which they disappeared. As it was my habit to sail out upon the 
ocean early every morning, I am certain that no other swarms than the 
above-mentioned ones occurred between June 25—August 19, 1898; 
and May 17-July 4, 1899. | 

Description of the Swarming. — The swarming commenced very early 
in the morning before sunrise, and soon vast numbers of the worms 
were to be seen swimming upon the surface of the ocean. Few or none 
of them were to be found in the shallow water near the shore of Log- 
gerhead Key, but at some distance to the westward of the island, where 
the water was between two and five fathoms in depth, they appeared in 
astonishing numbers. The bottom at this place is of coral-sand, and is 
covered with a sparse growth of Gorgonians and Nullipore Algze, while 
nearer the shore the bottom consists of living coral and coral-rock with 
but little sand. When first observed, at four o’clock in the morning of 
the days of the great swarms, the worms presented very much the ap- 
pearance shown in Figure 1, Plate 1. They swam with great activity 
and as near as possible to the surface of the sea. I estimate that there 
may have been about two worms to each square foot of the ocean’s 
surface. The worms were not uniformly distributed, however, but were 
scattered irregularly, sometimes congregating momentarily in wriggling 
masses, such as were likened by Agassiz, in the case of the Fijian 
Palolo, to “thick vermicelli soup.” These congregations are not due to 
any affinity for one another on the part of the worms, but are merely 
the result of accident, for each individual worm swims about quite inde- 
pendently of the others, and shows no tendency to remain in the presence 
of any other which it may chance to meet in its wanderings. The 


MAYER: STAUROCEPHALUS GREGARICUS. 3 


> 


worms continued to increase in numbers until the time of the rising of 
the sun, and then, as the light of the early morning fell upon them, a 
series of contractions came over the sexually ripe segments of each 
worm and the eggs or sperm were thus discharged into the water (see 
Figure 2, Plate 1). This contraction is often so sudden and so violent 
that the ripe segments are torn asunder, at short intervals, by the 
breaking of the cuticula, forming large rents through which the genital 
products escape. The 25-30 anterior segments of the worm contain no 
sexual elements, and take no part in the contraction, so that they re- 
main uninjured, and always retain their natural shape and appearance. 

After tke discharge of the sexual products the worms continue to 
swim near the surface for a considerable time, dragging their torn and 
contracted sexual segments after them. Sometimes, indeed, the con- 
traction causes the sexual segments to break away from the anterior 
portion of the worm, and they swim about, apparently suffering no in- 
convenience, although without a head. After the discharge of the eggs 
or sperm the sexual segments become very brittle, and a touch of the 
hand is often sufficient to cause them to break suddenly into small frag- 
ments. Jt seems not improbable that the torn and contracted sexual 
segments may eventually slough off from the 25-30 anterior ones, and 
that thus the life of the individual may be saved to perpetuate the 
species. This, however, is mere conjecture upon my part, for in 1898 
all of the worms which were confined in aquaria died during the course 
of the day without having thrown off their dishevelled posterior seg- 
ments ; and in 1899, when four of the worms were placed in a large 
aquarium the bottom of which was covered with sand and stones, three 
of the worms crawled under the stones, but all died within two days 
without having thrown off their contracted sexual segments. 

At 6.30 a.m. the worms began to sink down upon the sandy bottom 
of the ocean, and by nine o’clock in the morning none of them were to 
be seen. Large numbers of fish devour the worms during the time 
of swarming. 

There is little or no sexual color difference in the worms, both males 
and females being dull brick-red. The females, however, are sometimes 
of a duller and more yellowish tint than the males. The sperm is yel- 
low-buff or slightly pink in color, while the eggs are yellow or greenish 
yellow. The genital products escape in such quantity that the sea is 
rendered milky over wide areas, and long after the worms have disap- 
peared the eggs remain floating near the surface in visible windrows of 
yellowish color. 


4 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


In 1900 the last quarter of the moon occurs on June 19 and July 18; 
and as we do not yet know the limits of the lunar month in which the 
worm swarms, we may look for it within three days of either of the 
above dates along any of the Bahama or Florida reefs. It seems not 
improbable that it swarms annually on one day of the year, and that 
this day falls within three days of the moon’s last quarter in the month 
extending from June 15 to July 15. 

Description of the Adult Worm. —The genus Staurocephalus was 
founded by Grube, 1855, who has given a synopsis of the genus and a 
description of all of the then known species in the Jahres-Bericht der 
Schles. Gesell. fiir vaterl. Cultur., Bd. 56, pp. 109-115, 1878. Since 
then two new species have been described by McIntosh (85, pp. 231- 
235) ; and references to previously described species have been given 
by Ehlers, Verrill, and Andrews. 

Generic Characters. — Annelida, Polycheta, Family Nereide ; body 
vermiform, segments distinct. The head-lobes give rise to one or two 
pairs of jointed tentacles. When two pairs of tentacles are present, one 
pair arises from the side, and the other from the ventral surface. Eyes 
are sometimes present. The two first segments are without parapodia. 
The parapodia possess dorsal and ventral cirri. The dorsal cirrus is 
often unjointed, but sometimes possesses a short terminal segment. 
The ventral cirrus is shorter than the dorsal and is unsegmented. The 
posterior segment has two long dorsal and two short ventral cirri. 
The upper jaw consists of two simple, connected pieces. . The lower 
Jaw consists of two rod-like pieces which approach each other near the 
middle but diverge both in front and behind. (See Figures 20, 22, 26, 
27, Plate 3.) 

Specific Characters ; Adult Worm. —The worm is about 120-150 mm. 
in length; and may be even longer, for the posterior segment has not 
been observed. The segments are distinct, and there are about 17 
roetameres per centimetre of the worm’s length. The worm is about 
4mm. broad. The ventral surface is quite flat and a deep groove runs 
down its centre. The dorsal surface is arched, and the dorso-ventral 
diameter is about 3mm. There are no eyes, but the hypodermis cells 
of the front end of the prestomium bear a dark rosin-colored pigment, 
the presence of which may indicate a general sensibility to light. There 
are no lateral tentacles upon the head, but the ventral prestomium 
gives rise to two quite stiff tentacular cirri (see Figures 1-3, 9-12). 
These cirri consist each of but a single joiut. An axial nerve runs 
down the centre of each tentacle, and this nerve is surrounded by 


MAYER: STAUROCEPHALUS GREGARICUS. 5 


elongate hypodermis cells. The first metamere back of the head 
usual}y bears a pair of very rudimentary parapodia, each consisting of 
but a short dorsal and ventral cirrus. (Figures 11, 12.) In the worm 
shown in Figure 3, Plate 1, the first three segments back of the head 
bear very minute and undeveloped parapodia. The parapodia of the 
body segments are all similar each to each and consist in a well-developed 
dorsal cirrus, a central setigerous lobe, and a ventral cirrus that is 
shorter than the dorsal. (See Figure 13, Plate 2.) The setigerous lobe 
bears four kinds of setz. Most dorsal of all are three or four long 
curved, slender bristles having a delicately serrated edge (a, Figure 4, 
Plate 1). Immediately below these there are three or four smaller and 
more slender bristles, having flat spatula-shaped distal ends that 
exhibit sharp serrations (4, Figure 4). The ventral half of the setigerous 
lobe bears five or six setze of the sort shown in d, Figure 4 ; and most 
ventral of all there is a single thick, stiff bristle c, Figure 4. The 
blood of the worm is red, and there is a large red-colored blood sinus at 
the base of the dorsal cirrus of each parapodium. (See Figure 13.) 
The 25-30 anterior segments contain no sexual elements, these being 
found, however, in all of the more posterior segments. The blood 
vessels and nephridia of the sexually mature segments are much larger 
than are the corresponding organs in the anterior segments. The 
nephridia of the sexual segments evidently serve to carry off the eggs or 
sperm. The nephropores (np, Figure 13) are found at the base of 
each parapodium near the ventral surface. Sections of the worm were 
made, but the histology is so closely similar to that of other well-known 
Nereidz that we consider it unnecessary to enter into details concerning 
it. The constriction of the sexual segments is due to the powerful 
contraction of the circular muscles that lie immediately beneath the 
hypodermis. The sexes are separate, and there is no distinctly marked 
sexual coloration. The general color of the worm is dull brick-red or 
ochre-red, and there is a row of diamond-shaped dull white spots, one 
in each metamere, running down the mid-dorsal line (see Figure 10, 
Plate 2). Dark brown pigment is found around the orifice of each 
nephridium (np, Figure 13), and there are some indistinct brownish 
spots on the ventral side of the head (see Figure 12, Plate 2). These 
are not found, however, in all individuals, and probably do not function 
as eye-spots. 

Development. — The eggs and larve were killed in Perenyi’s fluid, 
stained in Kleinenberg’s hematoxylin, imbedded in paraffin and 
sectioned, the sections being usually of about 6.6 yw in thickness. 


6 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


After expulsion from the body of the worm the eggs float near the 
surface, where they are immediately fertilized. The eggs are quite 
large ; measurements of the embryos in the 16-cell stage gaye the 
diameter 0.36 mm. The segmentation is total and unequal. Four 
large yolk-laden macromeres are cut off from the four smaller yolkless 
micromeres. These latter then divide repeatedly and overlap the four 
macromeres, and thus the gastula is formed by epibole. Although my 
observations are far too incomplete for anything but general conclusions, 
it appears that the early stages of the segmentation are strikingly 
similar to those of Nereis as described and figured by Wilson (’92). 

Figure 5, Plate 1, represents an embryo in the 16-cell stage, which 
occurs about three hours after extrusion into the water. It will be seen 
that the large macromeres are heavily laden with deutoplasm-spheres, 
while the protoplasm of the micromeres is finely and uniformly vacuo- 
lated, giving the appearance, when seen in sections, of a delicate network. 
The centrosomes are of large size and stain quite deeply in hematoxylin. 

Figure 6 represents the condition of an embryo 94 hours old in which 
the blastopore (4p) is just about to be closed. It will be seen that a 
distinct segmentation cavity (sge) makes its appearance at this stage. 
This cavity may, however, be due to the action of reagents, and may 
not represent the natural condition. Unfortunately, all of my material 
having been killed in Perenyi’s fluid, I am unable to make any state- 
ments concerning this point. It will be noticed that some of the 
micromeres at this stage are beginning to exhibit large intracellular 
vacnoles, This is especially true of those cells about 180° away from 
the blastopore, and also of some in the immediate vicinity of the 
blastopore. In later stages this vacuolization affects all of the cells of 
the embryo, both those of the ectoderm and entoderm, and it is certainly 
true that for the first week of its life the larva owes its increase in size 
almost entirely to the remarkable development of intracellular and 
intercellular vacuoles. In this connection it is interesting to note that 
Davenport (’97) has shown that in the case of tadpoles the early growth 
is almost entirely due to the imbibition of water. Soon after this, when 
the embryo is about 94 hours old the blastopore closes, and the large 
deutoplasm-laden cells are completely enclosed by the micromeres. The 
embryos then become uniformly ciliated and swim about with consider- 
able rapidity. 

Figure 14, Plate 2, represents an embryo 24 hours old. Two eye- 
Spots are now beginning to appear, and between these there is a col- 
lection of greenish-colored cells. These cells stain very deeply in 


MAYER: STAUROCEPHALUS GREGARICUS. e 


Kleinenberg’s hematoxylin, and appear to be filled with a mass of 
deeply stained granules that may represent the coagulum of some fluid. 
Figures of these cells, in older larve, are shown in(g/) Figures 7, 8, 
Plate 1. I believe them to be glands, and they are probably homologous 
with the “frontal bodies” found by Wilson (’92, p. 421) in the larva of 
Nereis, and perhaps also with the “problematic bodies” observed by 
Mead (97, p. 256) in the larva of Amphitrite. Malaquin (93, p. 395, 
Plate XIV., Figures 12-16) has also found glands in a similar position 
in the head of the larva of Autolytus Edwarsi. 

Figure 15, Plate 2, represents a larva 3} days old, and Figure 7, 
Plate 1, shows a dorso-ventral section of the same. The eyes are now 
quite large, and the green patch representing the gland cells is very 
prominent. There are now three bands of cilia: a broad oral band, 
a narrow post-oral, and an anal band. Two sets of sete, consisting 
each of three bristles, have made their appearance immediately posterior 
to the post-oral band of cilia. These sete originate in folds of the 
hypodermis. A longitudinal dorso-ventral section (Figure 7) of the 
worm in this stage shows the very large gland cells (g/) of the head. 
The mouth (m) shows signs of being about to break through, although 
as yet it is not functional. The same may perhaps be said of the anus 
(an). The mid gut (sé) of the worm now consists of a delicate ento- 
dermal epithelium enclosing a mass of highly vacuolated cells laden with 
yolk spheres. 

Figure 16, Plate 2, shows a larva 5} days old, and Figure 17 illus- 
trates the character of the sete from the same worm. Most dorsal 
of all there is a single long seta (Figure 17, 4) and immediately be- 
low this there are two sete of the sort shown in Figure 17, a. 

Figure 18, Plate 3, shows a larva’ 10 days old. The worm is now 
0.5 mm. in length, and possesses three sets of sete. Until the end of 
the 15th day the larve are remarkable for exhibiting a strongly posi- 
tive phototaxis. They swim through the water at all depths, but 
large numbers of them are sure to be found clustered together in 
those parts of the aquaria where the light is strongest. 

At the end of the 15th day the cilia disappear, and the worms cease 
to swim through the water, and sink to the bottom. Figures 19, 20, 
represent a young worm that is 16 days old, and Figure 8, Plate 1, 
shows a dorso-ventral longitudinal section of the same. There are 
now four pairs of parapodia provided with dorsal and ventral cirri. 
A number of sensory hairs are found scattered over the preestomium, 
and the posterior segment of the body exhibits a pair of dorsal cirri. 


8 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


The mouth opens on the ventral surface, and a dorsal and ventral pair 
of “teeth” have made their appearance in the cesophagus (see Figure 
20). The worms are now about 0.8 mm. in length. Internal as 
well as external evidences of segmentation now appear (see Figure 8, 
Plate 1) and the dissepiments (ds) are complete. The walls of the 
mid gut are very thick and consist of large, irregularly shaped, highly 
vacuolated cells containing a number of yolk spheres. The cells of 
the cesophagus (oes) are of an epithelial character. The peripheral 
circular muscles and the deeper lying longitudinal muscle strands are 
beginning to appear, and the ventral nerve chain () is very apparent- 
In fact, the animal is no longer a larva, but is a young worm. 

Figures 21-23, 25-27, illustrate the condition of the worm at the 
end of the 26th day. There are now five pairs of parapodia, and the 
dorsal and ventral cirri of the posterior segment have become long and 
prominent (see Figure 23). The dorsal and ventral jaws of the cesoph- 
agus are shown in the side view of the head given in Figure 22. 
Figures 26 and 27 are views from above and from the side, respectively, 
of the dorsal pair of jaws. The condition of the ventral pair of jaws 
is still quite similar to that in the 16-day-old worm shown in Figure 
20. The worms are now 1.2 mm. long. They burrow readily 
beneath the surface of sand, but never swim through the water. 

Figure 24 shows the condition of a worm 34 days old. The animal 
is now 1.5 mm. in length, and there are still only five pairs of para- 
podia. The mature coloration is beginning to appear in two reddish- 
colored spots immediately back of the eyes. I did not succeed in 
rearing any worms beyond this condition, and know nothing of the 
mode of formation of the prestomium and cephalic cirri of the adult 
worm. It will be observed that in the young worm the mouth opens 
on the ventral surface and the prazestomium is supra-oral, while in the 
adult worm the preestomium and cephalic cirri are sub-oral (compare 
Figures 3 and 22). 


General Conclusions. 


Remarkably little has been written concerning the egg-laying habits 
of Polychetae. Wilson (’92, p. 371) states that the eggs of Nereis 
limbata and N. megalops are discharged at night while the animals 
are swimming upon the surface of the water. The egg-laying season 
extends at least from June until September. “The animals appear in 
abundance only on warm still nights, and even then are rarely found 


MAYER: STAUROCEPHALUS GREGARICUS. ) 


unless the water has been quiet for some days.” ‘ When the con- 
ditions are favorable, they come forth soon after dark and swim rapidly 
about at the surface, sometimes in almost incredible numbers.” 

It would probably be advantageous to any species of worm already 
possessed of some such egg-laying habits as those of Nereis to have the 
duration of the egg-laying period restricted to as short a time as pos- 
sible, and also to have it occur in that part of the year most favorable 
for the safety and development of the larvee. With equal numbers of 
mature individuals of two species (a) and (6), if (a) possess a long 
ege-laying period and (4) a short one, there will be more individuals 
of (6) discharging sperm or ova at any given moment than there will 
be of (a), whose breeding season is longer. Consequently the eggs of 
(6) will be more certain of fertilization, other things being equal, than 
those of (2). For example, if V represent the total number of individuals 
of species (@), and also of species (0) ; and if Z’ represent the duration 
of the egg-laying period of species (a) and ¢ that of species (4): then 


in any definite unit of time there will be oT individuals of species (a) 


, ie | eo 
discharging sperm and ova, while at the same time re individuals of 


species (>) will be engaged in the same act. Consequently, if the areas 
of the breeding-grounds of the two species are equal, there will be 


eV. 7, sede : 

[oes times as many individuals of species (4) discharging sperm 
or ova at any moment, in a unit of area, than there are of species (a) 
engaged in the same act. Then in an area containing m individuals of 


Species (a) there are a individuals of species (>). Therefore the 
t 
Vn — 1 
times as far as in the case of species (2). Hence the spermatozoze of 
fmt 
species (a) will be obliged to travel " ¢ times as far as those of 
/m — 1 
species (6). We see, then, that a shortening of the egg-laying season 
causes a greater concentration of breeding individuals, and therefore 
shortens the average distance that the spermatozoa must travel in order 
to fertilize the ova; and as spermatozoa cannot survive for any great 
length of time, this is an advantage to the species. In this connection 


average distance apart of the individuals of species (a) is 


10 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


it is interesting to notice that according to Wilson (’92, p. 372) the 
males of Nereis outnumber the females to a very remarkable degree, while 
in Staurocephalus gregaricus, and in the Pacific Palolo, the males and . 
females are about equal in numbers each to each. It is most essential 
for the perpetuation of the species that the fertilization of the ova 
should be insured. A very few males placed near to the females will 
insure this; but where the egg-laying period isa long one, and there 
are not often great concentrations of individuals, the males must out- 
number the females in order to make certain that the ova of any given 
female may be fertilized. 

The egg-laying period of Staurocephalus gregaricus occurred in 1898 
and 1899 upon days very close to the day of the last quarter of the 
June-July moon. At this time, in the Tortugas, Florida, the summer 
is well established, the trade winds are no longer steady or boisterous, 
and the calm weather that precedes the hurricane season has set in. 
It is interesting to notice that very similar meteorological conditions 
prevail in Samoa and Fiji, in October and November, — the months of 
the swarming of the Palolo. 

My friend, Dr. Charles B. Davenport, has called my attention to the 
fact that the advantages derived from a short egg-laying season are in 
some measure offset by the circumstance that under such conditions a 
large number of young larve are suddenly produced, and that therefore 
the struggle for food must be greatly increased. To counterbalance 
this difficulty, however, we have the interesting fact that while the eggs 
of Nereis contain but little yolk, the eggs of Staurocephalus gregaricus 
are heavily laden with yolk material. 

When we learn more concerning the egg-laying habits of Annelids, 
there will no doubt be a number of species found that possess such 
swarming habits as those of Nereis, and perhaps a few may be dis- 
covered in which the breeding season is as short as in Staurocephalus 
gregaricus and Palolo viridis. In 1893, while acting as assistant to Dr. 
Alexander Agassiz upon the “ Wild Duck” Expedition to the Bahama 
Islands, I had the opportunity of observing the swarming of an Annelid. 
We were anchored off Watlings Island (San Salvador) on the night of 
January 15, and in Clarence Harbor, Long Island, on the night of 
January 16. On both of these nights the surface of the sea was covered 
by thousands of little Annelids. They were translucent, and had large 
red eyes. They appeared to be congregating for breeding purposes, and 
were breaking into pieces, so that we often found fragments 50 mm. in 
length swimming about without a head. The last quarter of the moon 


MAYER: STAUROCEPHALUS GREGARICUS. i git 


occurred on January 9, 1893, and their swarming probably had no 
relation to this event. 

Among worms, where certain segments of the body became sexually 
mature while others remain immature, or non-sexual, we find an inter- 
esting series of gradationsin complexity. Beginning with Staurocepha- 
lus gregaricus, where the sexual and non-sexual segments are exactly 
alike in external appearance, and where the entire worm swims at the 
surface at the breeding period, the next advance in complexity is met 
with in Palolo viridis, where, according to Friedlander (1898) the non- 
sexual segments are very different in appearance from the sexual, and 
where the sexual segments break off from the anterior portion of the 
worm and swim about during the egg-laying period without a head. 
Most complex of all are the cases of Autolytus, Filigrana, Myriana, 
Procerza, Syllis, etc. (see A. Agassiz, 62; Malaquin, ’93, etc.), where 
the sexual segments acquire a head, and eventually become free swim- 
ming worms, thus producing an alternation of generations. 

It seems probable that Staurocephalus gregaricus and Palolo viridis 
have independently acquired quite similar breeding habits through the 
agency of similar influences of natural selection ; although it must still 
be admitted that there remains a possibility that both worms may have 
descended from a remote and common ancestor that possessed some such 
breeding habits. 

The following table will serve to illustrate the principal points -of 
relationship in the breeding habits of the two worms : — 


Tar Atiantic “ PaLowo.” Tue Paciric PaLo.o. 


Palolo viridis, Gray, 1847. 


Staurocephalus gregaricus, Mayer. 
Lysidice viridis, Cotiin, 1897. 


On July 9, 1898, and July 1, 1899, 
the worm swarmed in vast numbers, 


The worm swarms in great num- 
bers, for breeding purposes, at Samoa 


for breeding purposes, at the Dry 
Tortugas Islands, Florida. The last 
quarter of the moon occurred on July 
10, 1898, and June 29, 1899. 


The 25-30 anterior segments of 
the worm contain no sexual ele- 
ments, the eggs or sperm being 
found in the posterior body seg- 
ments. The anterior segments, how- 


and Fiji, upon the mornings of the 
day of, and the day preceding, the 
last quarter of the October and No- 
vember moon. (See Whitmee, 1875 ; 
Friedlander, 1898.) 


According to Friedlander, 1898, 
a number of the anterior segments of 
the worm contain no sexual elements, 
these being found in the posterior 
body segments. The anterior seg- 


12 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


ever, are similar to the sexually 
developed posterior ones in external 
appearance. 


The entire worm swims at the sur- 
face during the breeding period. 


The eggs or sperm are extruded 
from the sexual segments by a series 
of contractions. They pass out into 
the water not only through the ne- 
phridial openings, but also through 
rents and tears in the body wall of 
the worm, which are often produced 
by the violence of the contractions. 
This action usually occurs soon after 
sunrise. 


There is no well-marked sexual 
color difference, both males and fe- 
males being brick-red, or ochre-red. 
The eggs are greenish-yellow and the 
sperm buff-pink. 


The males and females are about 
equal in number each to each. 


The segmentation is total and un- 
equal, and the gastula is formed by 
epibole. The larva is telotrochal. 
The setee appear very early in devel- 
opment. The larva possesses a pair 
of eyes, and remarkably large ecto- 
dermal, cephalic glands. 


Harvarp University, April, 1899. 


ments are of greater breadth and less 
length than are the sexually devel- 
oped posterior segments. (See Fig- 
ure by Friedlander.) 


The posterior or sexual segments, 
only, swim at the surface during the 
breeding period. The anterior por- 
tion of the worm remains below. 


The eggs or sperm are extruded 
from the sexual segments by a series 
of violent contractions. They pass 
out into the water not only through 
the nephridial openings, but also 
through rents and tears in the body 
wall of the worm, produced by the 
violence of the contractions. This 
action usually occurs soon after sun- 
rise. (See McIntosh, 1885 ; A. Agas- 
siz, 1898.) 


The inales are brown, and the fe- 
males dark green. The eggs are 
green. (See Whitmee, 1875; McIn- 
tosh, 1885.) 


The males and females are about 
equal in number each to each. 


The development is unknown. 


MAYER: STAUROCEPHALUS GREGARICUS. 13 


BIBLIOGRAPHY. 


Agassiz, A. 

°62. On Alternate Generations in Annelids, and the Embryology of Autolytus 
cornutus. Boston Journ. Nat. Hist., Vol. VII. pp. 384-409, Plates 
IX.-XI. 

Agassiz, A. 

798. Islands and Coral Reef of the Fiji Group. American Journ. Sci., Ser. 

4, Vol. V. p. 123. 
Andrews, A. E. 

°91. Report on Annelida Polycheta of Beaufort, North Carolina. Proc. U.S. 

National Museum, p. 288. 
Collin, A. 

797. Ueber den Bau der Korallenriffe, etc., von Dr. Augustin Kramer, 
Marinearzt, nebst einem Anhange: Ueber den Palolowurm von Dr. A. 
Collin. ' Kiel und Leipzig, Verlag von Lipsius und Tischer. 

Davenport, C. B. 
97. The Role of Water in Growth. Proc. Boston Soc. Nat. Hist., Vol. 
XXVIII. No. 3, pp. 73-84. 
Ehlers, E. 
°64~68. Die Borstenwiirmer, pp. 422-442. (Staurocephalus.) 
Ehlers, E. : 

°87. Florida-Anneliden. Mem. Mus. Comp. Zool]. Harvard Coll., Vol. XV. 

pp: 64, 68. (Staurocephalide.) 
Friedlander, B. 

°98. Ueber den sogenannten Palolowurm. Biolog. Centralblatt, Bd. XVIII. 

pp. 337-357, 2 Figs. 
Gray, Vo 12 

47. An Account of the Palolo, a Sea Worm eaten in the Navigator Islands. 

Proce. Zodl. Soe. London, pp. 17-18. 


Grube, A. E. : 
55. Archiv fiir Naturgesch., Jahrg. 21, p. 97 (Genus Staurocephalus). 
Grube, AE. 
°78. Fortsetzung der Mittheilungen iiber die Famile Eunicea. Jahres-Bericht 
der Schles. Gesell. fiir vaterl. Cultur., Bd. LVI. pp. 109-115. (Stauro- 
cephalide.) 


14 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


McIntosh, W. C. \ 
°85. Report on Annelida. Challenger Reports, Zool., Vol. XII. Stauro- 
cephalus, pp. 231-235; Palolo viridis, pp. 257-261. 


Malaquin, A, 
°93. Recherches sur les Syllidiens, pp. 1-477, 18 Pl’s. L. Danel, Lille. 


Mead, A. 
°97. The Early Development of Marine Annelids. Journ. Morphology, Vol. 
XIII. pp. 227-826, Plates X.-XIX., Figs. in text. 


Verrill, A. E. 
’°82. New England Annelida. Trans. Connecticut Acad. Sci. Vol. IV. pp. 
285-324 e, Plates III.-XII. 
Webster, H. E. 
"79. On the Annelida Cheetopoda of the Virginian Coast. Trans. Albany 
Inst., Vol IX. pp. 202-269, 11 Plates (Staurocephalus). 


Whitmee, S. J. 
"75. On the Habits of Palola viridis. Proc. Zodl. Soc. London, pp. 496-502. 
Wilson, E. B. 
°92. The Cell-Lineage of Nereis. Journ. Morphology, Vol. VI. pp. 361-480, 
Plates XIII.-XX., Figs. in text. 
Wilson, E. B. 


°98. Considerations on Cell-Lineage and Ancestral Reminiscence. Annal. 
N. Y. Acad. Sci., Vol. XI. pp. 1-27, Figs. im text. 


—————————— 


Fig. 


. 


Fig. 


Fig. 


Mayer. — Staurocephalus gregaricus. 


go 


On 


S 


PLATE 1. 


Staurocephalus gregaricus, nov. sp., natural size, swimming near the sur- 
face of the water before the rising of the Sun. The terminal segment 
has broken off, and the genital products are escaping through tlie 
orifice. 

Staurocephalus gregaricus, natural size, showing the worm in the act of 
expelling its sexual products. The eggs or sperm escape into the 
water through the nephridial tubules, and also through rents and tears 
in the cuticula of the worm. This contraction usually occurs immedi- 
ately after the rising of the Sun. f 

Side view of the head end of the worm; magnified. (m) mouth, \- Qnwds 

Sete of the parapodia. (a) are most dorsal; (b) next; (d) next; and (ce) 
most ventral. See Figure 15, Plate 2. 

Section of an embryo in the 16-cell stage, magnified 100 diameters. Age 
3 hours. 

Section of an embryo in the gastrula stage immediately before the closure 
of the blastopore. (bp) blastopore; (sgc) segmentation cavity. Age 
94 hours. 

Longitudinal dorso-ventral section of an embryo 34 days old, magnified 
100 diameters. (an) place where the anus is destined to appear; (g/) 
head glands ; (m) place where the mouth is destined to break through ; 
(oes) cesophagus. (sf) mid gut, or “stomach.” The ege-membrane 
persists as a larval cuticula. 

Longitudinal dorso-ventral section of a young worm 16 days old. (an) 
anus ; (ds, ds, ete.) dissepiments; (g/) head glands; (m) mouth; (n) 
ventral nerve-chain ; (oes) esophagus ; (st) cavity of mid gut. 

Longitudinal dorso-ventral section through the head region of a mature 
worm, showing tentacular cirrus and muscular pharynx. The intes- 
tine of the sexually mature worm is practically empty. (m) mouth. 
(n) ventral nerve-chain. 


PLATE. 1. 


_ MAYER-ATLANTIC PALOLO” 


SNWIMAZ 


SY 


REA 


ee 


) ae ds ds 


Nae 

S 
R~ 
& 


B. Meisel lith Boston. 


AGM. del. 


Mayer. — Staurocephalus gregaricus. 


Fig 10. 


Fig. 11. 
Fig. 12. 
Fig. 13. 


Fig. 14. 


Fig. 15. 
Fig. 16. 


Figs. 17. 


PLATE 2. 


Dorsal view of Staurocephalus gregaricus, nov. sp., magnified 2 diameters. 
Showing the sexual segments contracted after the ie of the 
genital products. 

Dorsal view of head, showing mouth opening. Magnified. 

Ventral view of head. Magnified. 

Side view of parapodium of the 40th segment from the head of the worm. 
(np) nephropore. 

Larva one day old. Showing the green-colored gland cells between 
the eyes. 

Larva 34 days old. (gl) head glands. 

Larva 54 days old. 

(a) and (4) sete of a larva 5} days old. 


MAYER-ATLANTIC‘ PALOLO" ' PLATE, 2. 


| 
: 
| 
J 


AGM al. B Meisel lith Boston. 


oO 


7 reo : r 

hve a pone 
Pe eT ns CRE 

P71 pee Tr 
a o 


Fig. 
Fig. 
Fig. 


Fig. 
Fig. 


Fig. 
Fig. 


Fig. 
Fig. 


Fig. 


Mayer. — Staurocephalus gregaricus. 


18. 


19. 


20. 


21. 
22. 


23. 
24. 


25. 
26. 


27. 


PLATE 3. 


Larva of Staurocephalus gregaricus, nov. sp., 10 days old. 

Dorsal view of a young worm 16 daysold. The animal now ceases to 
swim through the water, but will readily burrow beneath the surface 
of sand upon the bottom of the aquarium. Length 0.8 mm. 

Ventral view of the head end of a young worm 16 days old, showing the 
“jaws” of the esophagus. 

Dorsal view of a worm 26 days old. Length 1.2 mm. 

Side view of a worm 26 days old, showing the “‘ jaws ” in the csophagus. 
(m) mouth. 

Side view of the posterior segment of a worm 26 days old, showing cirri. 

Dorsal view of a worm 34 days old, showing the beginnings of the mature 
coloration immediately back of the eyes. Length 1.5 mm. 

Seta from a worm 26 days old. 

Dorsal view of the dorsal “jaws” from the esophagus of a worm 26 
days old. 

Side view of the dorsal “ jaws ” from the esophagus of a worm 26 days 
old. 


Ge as) 

< Ee 

i = 
e714 aa) 
Pac! 

I 

2 

Ay 

iS 

Looe | 

a 

B 

eta 

(a : 

a tal 

KS a 

<i = 


Bulletin of the Museum of Comparative Zoology 
AT HARVARD COLLEGE, 
Vou. XXXVI. ~ No. 2: 


SOME NORTH AMERICAN FRESH-WATER RHYNCHO- 
BDELLIDH, AND THEIR PARASITES. 


By W. E. CASTLe. 


Wirn Erent PLATeEs. 


CAMBRIDGE, MASS., U.S. A.: 


PRINTED FOR THE MUSEUM. 
Avcust, 1900. 


AUG 29 1900 


No. 2.— Some North American Fresh-Water Rhynchobdellide, 
and their Parasites.1 By W. E. CASTLE 


CONTENTS. 
PAGE 
I. Introduction. ; 18 e. Nervous System . 
ieeeWethodsigaies. ss ks 18 4. Glossiphonia heteroclita L. 
Ill. Classification 20 a. Habitat, Form, Size, 
Key to Species 20 Color . See eon 
IV. Description of Species 21 6. Rings, Somites, Eyes, 
1. Glossiphonia stagnalis Li 21 Suckers, etc. 
a. Habitat, Form, Size, c. Reproductive Organs . 
Color . é = PAL d. Digestive Tract . 
b. Rings, Somites, Eyes . 22 e. Nervous System . 
c. Dorsal Gland, Suckers 238 5. Glossiphonia elegans Ver- 
d. Reproductive Organs . 24 Tyee ne ; 
e. Digestive Tract . 26 a. Habitat, Size, Colors 
f. Nephridia 27 6. Surface, Rings, Somites, 
g. Nervous System . 28 Eyes, Suckers . 
h. Metamerism 28 c. Reproductive Organs . 
(1) Number of Somtes 28 d. Digestive Tract . 
a. Structure of a Typ- e. Nephropores, Nervous 
ical Ganglion . 29 System Soa 
8. Fused Ganglia . 29 6. Glossiphonia parasitica 
(2) Somite Limits 31 Saye a ces. © 
2. Glossiphonia fusca, sp. nov. 34 a. Habitat, Form, Shee 
a. Habitat, Form, Size, b. Rings and Somites . 
Color . Se tes BE ce. Eyes, Mouth, Oral 
b. Rings, Somites, Eyes, Sucker 
Suckers SG d. Reproductive Organs : 
ce. Reproductive Organs eS: e. Digestive Tract . 
d. Digestive Tract . 37 f. Nephropores, Nervous 
e. Nervous System . 38 System 
8. Glossiphonia i sp. g. Papille, Coloration . 
nov. : 39 (1) Var. plana . 
a. Habitat, Hara sire (2) Var. rugosa 
Color . 39| V. Mutual Relationships of the 
b. Rings, Somites, yer Species Described . 
Suckers 40} VI. Parasites . 


ce. Reproductive Organs : 
d. Digestive Tract . 


41 | Bibliography she 
41 | Explanation of Plates 


1 Contributions from the Zodlogical Laboratory of the Museum of Comparative 
Zodlogy at Harvard College, E. L. Mark, Director, No. 112. 


VOL. XXxvI. — No. 2. 


18 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


I. INTRODUCTION. 


In the fall of 1897 a small leech, which is very abundant in the ponds 
about Cambridge, Massachusetts, was selected as an object for study in 
the class in Microscopical Anatomy in Harvard University. This selec- 
tion brought under my observation a rather large number of leeches 
living or prepared in one of various ways, and gave occasion to the 
studies out of which this paper has grown. The kindness of friends has 
greatly aided me in obtaining material. In this connection my thanks 
are due to Mr. G. M. Allen, who sent me living leeches from the White 
Mountains in New Hampshire and also collected for me much valuable 
material in Massachusetts; to the Museum of Comparative Zodlogy for 
the privilege of studying its collection of leeches ; to Professor James G. 
Needham, who sent me collections made in New York and Illinois, and 
also loaned me for study the collection of leeches belonging to Lake 
Forest University ; to Dr. C. A. Kofoid, who obtained for me leeches 
from Havana, Illinois; to Mr. R. H. Johnson, for specimens collected in 
Lake Chautauqua, N.Y.; and last but not least, to Professor E. L. Mark 
and Dr. Otto Zur Strassen, who collected and preserved for me indi- 
viduals of several European species. 

Professor Whitman, who has given so much attention to the study 
of leeches, several years ago (’91*) pointed out the inadequacy of all 
descriptions then existing of our North American species of “ Clepsine,” 
showing that the descriptions in question were based on characters alto- 
gether too superficial and unreliable. Whitman himself presented a 
model in his description of “Clepsine plana;” but as this has not been 
followed by any similar account of our other species, I have thought it 
worth while to record in this paper some observations of my own, to- 
gether with the views regarding the external morphology and relation- 
ships of our common species, to which studies, chiefly anatomical, have 
led me. 


II. METHODS. 


For the study of the general anatomy of a leech and particularly for 
the study of its external morphology, it is important to have both living 
animals and those which have been killed in a good state of extension. 
Of the former I have been fortunate enough to obtain an abundance ; in 
preparing the latter I have found very serviceable the method recom- 


CASTLE: NORTH AMERICAN RHYNCHOBDELLID#. 19 


mended by Lee (94, p. 17) of stupefying with carbonated water.t The 
animals are placed in a Stender dish and covered with water from a 
“soda siphon.” As soon as they are thoroughly stupefied, they should 
be quickly transferred to the killing fluid, which is best used warm, not 
boiling hot, but heated to about 70°C. A stay of from two to five 
minutes in the carbonated water usually suffices to stupefy the smaller 
species enough for successful fixation, and indeed is better than more 
prolonged treatment. For if the animal still possesses a slight degree 
of irritability, it will usually straighten out in the warm killing fluid 
and die in a better state of extension than it was in before. The large 
species require a much longer treatment with the carbonated water. 
The best reagent to use in killing animals for whole preparations is, in 
my experience, Perenyi’s fluid, which leaves the animal well extended 
and renders it clear and transparent. It has the property of removing 
pigment from the body, particularly the darker sorts of pigment. For 
instance, I have noticed that in killing the beautifully variegated Glossi- 
phonia parasitica with this fluid, the green and brown spots often dis- 
appear entirely ; while the yellow and orange spots remain conspicuous. 
This quality is sometimes an advantage, sometimes a disadvantage. If 
one wishes to preserve the color-pattern unimpaired, he would do well 
to use a fluid containing picric acid, which seems to have the property 
of fixing the pigment ; or, better still, use formaldehyde both as the 
killing and as the preserving fluid. 

Flemming’s fluid is perhaps, on the whole, the best fixing fluid to use 
in preparing sections; corrosive sublimate is also good; Perenyi’s fluid 
is for this purpose not to be recommended, except for the study of the 
gross anatomy of the central nervous system, which it makes very clear 
by bringing out nerves and fibre tracts in strong contrast to their con- 
nective-tissue sheaths. 

Iron hematoxylin is the best stain which I have tried for sections. 
For whole preparations, animals should be heavily stained with carmine 
and then pretty thoroughly decolorized. I find Mayer’s hydrochloric 
acid carmine (70% alcoholic) very convenient and serviceable, as it stains 
powerfully and there is no danger of maceration of tissues, however long 
the stain is allowed to act. 

Decolorizing is best done with alcohol pretty strongly acidulated, as 
greater contrasts are thus obtained. I use 1% hydrochloric acid in 70% 


1 This method of stupefaction is also very useful in the study of the living 
animal, for the leech may be kept entirely motionless in the carbonated water 
within a live-box for hours, and then be revived by placing it again in fresh water. 


\ 


20 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


alcohol, allowing it to act until the specimens have a light rose color, 
then wash well in neutral alcohol (90%), clear in cedar oil, and mount 
in balsam. 


III. CLASSIFICATION. 


Leeches of the family Rhynchobdellidz may be distinguished from all 
others by the fact that they possess an exsertile proboscis ( pr’d., Figure 1), 
with the aid of which they obtain their food, for they are entirely with- 
out jaws such as the medicinal leech possesses. Our common North 
American species of this family belong to the genus Glossiphonia John- 
son (16), better known to many by its synonym Clepsine Savigny 
(20). Leeches of this genus have usually a broad flat body, which, 
when the animal is disturbed, is rolled into a ball. Each somite con- 
sists typically of three distinct rings; but the somites at the ends of the 
body always contain a smaller number of rings. 

These leeches are found in the shallow water of ponds and rivers 
underneath stones, sticks, or leaves, or adhering to the bodies of their 
hosts. The smaller species feed upon snails, crustacea, or other small 
fresh-water animals; the larger species are known to feed upon turtles, 
to whose shells they are often found attached. They probably suck the 
blood of other aquatic animals also. 

The following key may aid in distinguishing the species to be 
described : — 


Key to Species. 


A. Crop diverticula a single pair (after a full meal the animal may have 
five more pairs, inconspicuous, and situated anterior to the prin- 
cipal pair) ; male and female genital pores separated by a single 

body ring ; rings without metameric markings in the living animal. 

1. Eyes two, distinct ; a conspicuous yellowish brown chitinous 
spot on the neck dorsally . . . . . . G. stagnalis (p. 21) 
2. Eyes two, inconspicuously pigmented or entirely without pig- 
ment ; no chitinous spot on the neck ; body extremely slender and 
transparent . . .. . . . « ~ | G. elongata (p39) 

B. Crop diverticula six pairs ; tice and female genital pores separated 
by a single body ring or else united. 

3. Eyes two, the middle (sensory) ring of each somite marked 
throughout the greater part of the body by a transverse row of 
whitish spots; .. 0 . ts 2 1 (= sa) Geer Gasca 


CASTLE: NORTH AMERICAN RHYNCHOBDELLID A. 21 


4, Eyes six, the first pair small and close together, the others 
farther apart; rings without metameric markings, or with dark 
pigment on the anterior ring of each somite. 

G. heteroclita (p. 42) 
C. Crop diverticula seven pairs ; male and female genital pores separated 
by two body rings. 

5. Hyes six, distinct, in two parallel rows; a conspicuous longi- 
tudinal band of dark pigment on either side of the median plane 
dorsally, and a fainter one Salar: ; mMeconspicuous papille on 
the dorsal surface . . . - - « + G. elegans (p. 46) 

6. Eyes apparently a Avale pair, far forward on the head and 
confluent ; back distinctly papillose. A large species, often found 
ouiturtles 5°, . - - - - « - - «  G. parasitica (p. 51) 


IV. DESCRIPTION OF SPECIES. 


1. Glossiphonia stagnalis Liynaus (1758). 
Plate 1, Figs. 1, 3; Plate 2, Fig. 4; Plate 3, Figs. 7-10, 12; Plate 8, Fig. 34. 


Hirudo stagnalis Linneus (1758); H. bioculata O. F. Miiller (1774); Clepsine 
bioculata Savigny (’20); C. modesta Verrill ("72); C. submodesta Nichol- 
son (’73). 

a. Hasitat, Form, Sizp, Conor. 


This species is found in Kurope, the adjacent parts of Asia and Africa, and 
in North and South America. As one might expect in the case of so cosmo- 
politan a form, much has been written about it, but its external morphology 
has never been carefully and accurately analyzed, and published accounts of its 
internal anatomy contain a number of errors or omissions, some of which | 
hope to rectify. 

The general form of the body as seen in dorsal view, when partially extended, 
is shown in Figures 1 and 4. The body is broadest posterior to its middle and 
thence tapers gradually toward both ends. The head, which is only slightly 
wider than the neck, is evenly rounded in front (Figure 3) ; dorso-ventrally 
the body is very much flattened, especially when at rest. The animal is very 
active in its movements and can greatly elongate its body so as to become more 
than ten times as long as it is broad. The largest individuals measure as 
follows : — 

Length, fully extended, 20-25 mm. ; at rest, 8-10 mm. 

Width, fully extended, about 2 mm.; at rest, about 5 mm. 

Color, flesh-color or grayish. Small individuals are usually quite clear and 
transparent, but larger ones are apt to be more or less opaque. This opacity, 


22 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 


as well as the general grayish tint which the body often has, is due to the 
presence in varying proportions of two different sorts of pigment cells. Those 
of one kind, which might properly be called reserve-food cells, may be found 
in the deeper parts of the body of all well-nourished individuals. They are. 
large rounded cells, with an excentrically placed nucleus, their cytoplasm being 
filled with rounded, highly refractive granules often nearly as large as the 
nucleus. By reflected light these granules appear of an orange-brown color, 
Osmic acid browns slightly, but does not blacken them. Corrosive-acetic or 
picro-nitric mixtures make their composite nature apparent. An outer shell 
of darker, brownish substance appears surrounding usually one, sometimes 
two or three perfectly clear spherical inclusions. Perenyi’s fluid, which is 
very strong in nitric acid, if allowed to act for about an hour, destroys almost 
every trace of the granules, the outer shell being the last part to disappear. 
Absolute alcohol acts in a similar way, but more slowly. 

Graf (99) has figured the granules accurately (see his Figures 87 and 102), 
but interprets their structure somewhat differently, regarding the clear portions 
as cavities; hence he speaks of the granules containing them as ring-shaped 
structures. 

I at first supposed the clear portion to be a central core unaffected by the 
killing fluid, but abandoned this idea when I discovered two or more of them 
in different parts of the same granule. It seems to me that the outer part of 
the granule, which possibly contains some fatty material, as the osmic acid test 
indicates, is laid down upon a central core of a different substance which 
dissolves much more readily in acid solutions. So much my preparations 
indicate, but do not prove conclusively. Further study should be given to 
these interesting structures, doubtless a reserve-food product, which reminds 
one of the structures found in the seed of the Castor-oil Bean (Ricinus). 

The second sort of pigment cell found in this species belongs to Graf’s (99) 
category of “excretophores.” They occupy a superficial position in, or just 
under, the epidermis, and are slender, thread-like, branched (structures) of a 
dark-brown color. They are especially abundant in animals which have been 
kept for some time in well-lighted aquaria. Graf believes that pigment cells 
of this sort become detached as leucocytes from the wall of the body cavity, 
take up excretory products in the deeper parts of the body, especially in the 
neighborhood of the blood vessels, and then by amoeboid movements make 
their way to the surface of the body, there to disintegrate. 


b. Rines, Somites, Eyes. 


External rings, rounded. and distinct ; sixty-seven in number, counting two 
narrow rings at the posterior end of the body (64 and 66, Figure 4, Plate a) 

Somites, thirty-four, as in all species of Glossiphonia. Somites VI.—XXIV., 
triannulate (Figure 4); all other somites show more or less abbreviation.! 


1 Throughout the descriptive part of this paper I shall speak of those somites 
which contain fewer than three distinct rings as “abbreviated” or “reduced.” I 


CASTLE: NORTH AMERICAN RHYNCHOBDELLIDA. 23 


Somites 1. and 1. are together represented by a single broad ring (Figures 3, 
4), which, however, is sometimes subdivided by a shallow furrow (Figure 7, 
Plate 3). 

. Somites m1. and Iv. consist each of a single ring, the latter forming the pos- 
terior boundary of the oral sucker (Figure 3, Plate 1; Figure 7, Plate 3). 

Somites xxv. and XxvI. consist each of two rings, a broad followed by 
a narrow one (63 and 64, 65 and 66, Figure 4, Plate 2; Figure 34, Plate 8). 
The narrow ring of somite xxvi., however, is often so completely fused with 
the broader ring which precedes it as to be scarcely distinguishable. 

‘Somite xxvuI. consists of a single broad ring, crowded back to a position 
lateral and posterior to the anus (67, Figures 4, 34, and A). 

Somites XXVIIIL-XXXIV. are not represented by external rings; in the 
central nervous system, however, we shall find clear evidence of their separate 
existence, A further discussion of the metamerism will be deferred until the 
nervous system has been described. 

Eyes, two, large and distinct, lying in the anterior part of ring 3 and ex- 
tending forward into the posterior part of ring 2 (Figures 4, 7). 


c. DorsaL GLAND, SUCKERS. 


Dorsal Gland. — Between the twelfth and thirteenth rings (that is, between 
the anterior and middle rings of somite vim.) on the mid-dorsal surface of the 
arimal, is a structure (gl. d., Figures 4, 7) peculiar to this species, though accord- 
ing to Apathy (88*) its homologue is found in some other species, either as a 
functional structure in the embryo, or as an inconspicuous rudiment in the 
adult. It consists of a rounded, wart-like, yellowish-brown, cuticular plate, 
often surrounded by a ring of substance similar but lighter in color, probably 
because less well hardened. These structures are secreted by a patch of 
high columnar epidermal cells, which in the embryo, according to Apdthy, 
form a sort of byssus gland serving to attach the young to the under side of 
the mother before the suckers at the ends of the body become functional. In 
the adult the organ has no known function, thongh it forms a favorite place of 
attachment for a certain colonial protozodn of the genus Epistylis. 


do so, however, without feeling at all certain that the terms are strictly appli- 
cable in all cases or even in a majority of cases. I have elsewhere (Castle, 1900) 
expressed the opinion that the leech somite consisted primitively of a single ring. 
If this is so, it may well be that the somites commonly spoken of as abbreviated 
have really never attained the triannulate condition. (Moore, 1900, has expressed 
a similar view since this paragraph was written.) Nevertheless the term is a con- 
venient one to express deviation from the typical condition of the somite in the 
direction of a shortening of it. In this sense the term will be employed in this 
paper. 

1 Budge (’49) likewise represents the eyes in the anterior part of ring 3. 
Apathy (’88*), however, counts the ocular ring the fifth, emphasizing subdivisions 
which can occasionally be seen in the most anterior rings. (Compare his Figures 4 
and 10 with my Figures 3 and 7.) 


24 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


The oral sucker (suc. or., Figure 7) lies on the ventral side of the head, within 
the limits of rings 1-3 (somites I.-Iv.). 

The mouth (or., Figure 7) opens anterior to the middle of the oral sucker as 
well as anterior to the eyes. 

The posterior sucker (act., Figures 1, 4), also ventral in position, is slightly 
longer than broad. Average dimensions for the largest individuals are :— 
length, 1.31 mm. ; width, 1.24 mm. 


d. REPRODUCTIVE ORGANS. 


The male genital pore (po. @, Figure 4) lies in a mid-ventral position between 
rings 24 and 25; that is, between the anterior and middle rings of somite x11. 
The female genital pore (po. 9, Figure 4), which is a broad transverse slit, . 
lies just one ring behind the male pore, between rings 25 and 26, the middle 


and posterior rings of somite x11.) 
XIII. XVIII. 


Testes (Figure 4, te.), six pairs, placed intersegmentally in somites er = 
The size and appearance of the testes vary considerably with the seasons. In 
the fall and early spring they are generally large and their outlines more or 
less irregular, for they adapt themselves to the spaces left them among the 
dorso-ventral muscles and other deep-lying organs. The testis wall is quite 
thick on its dorsal, ventral, and lateral aspects, but somewhat thinner on its 
median aspect. It is lined with a loose germinal epithelium of spindle-shaped 
cells, except at its dorso-median angle, where there is a small patch of ciliated 
epithelium continuous with that of the vas efferens. 

Male genital ducts. — The vas efferens is a short, delicate tube, which leads 
dorsad and cephalad to join a longitudinal duct similar in structure to itself 
and only slightly larger, the proximal or collecting part of the vas deferens 
(Figure 4, va. df.). Anterior to the first pair of testes, that is, about on the border 
between somites x11. and x11., the collecting portion of the vas deferens bends 
sharply toward the median plane of the body and passes between the strong 
dorso-ventral muscles, which, like a row of pillars, mark off on each side the 


1 I am unable to find in any published account an explicit statement as to the 
position of the genital pores in this species. Budge (’49) figures the male pore in 
the posterior third of ring 25 and says, “ Gegen den 25 Ring findet sich die sehr 
feine miannliche Geschlechtséffnung.”” He does not figure the female pore, but 
says (p. 100), ‘‘Ungefahr am 27. Leibesringe die 4ussere [female] Geschlechtsoff- 
nung liegt.” This would make the genital pores distant from each other about two 
rings, which, however, is incorrect. 

Ludwig (’86) incorrectly describes the position of the genital pores for the 
entire genus ‘‘Clepsine” as follows (p. 781) ‘“‘mannliche Geschlechtséffnung 
zwischen dem 25. und 26., weibliche zwischen dem 27. und 28. Ringel.” This state- 
ment rests upon two erroneous assumptions, first, that the number of distinct rings 
is the same in the head region of all species, and, secondly, that the genital pores 
are always two rings apart. In only two of the six species described in this paper 
are the genital pores separated by two rings. 


CASTLE: NORTH AMERICAN RHYNCHOBDELLIDA. 25 


lateral limits of the median lacunar space. This space the vas deferens enters in 
company with the ducts of the salivary glands, which here pass inward to join 
the base of the proboscis (Figure 1, gl. sal.) Having reached the median lacuna, 
the vas deferens turns backward, running usually ventral and lateral to the diges- 
tive tube and parallel with the course of its collecting portion. In the median 
lacuna it winds about more or less, or may even cross into the opposite half of 
the body as a result of its being crowded for room either because of its own dis- 
tended condition or from the condition of other organs in its vicinity. As it runs 
backward it widens into a spacious seminal vesicle (Figure 4, vs. sem.), and its 
epithelial lining ceases to be ciliated. The dimensions of the seminal vesicles 
vary with the amount of sperm stored in then being capable apparently of 
great enlargement. Sometimes the vesicle runs back as far as the pair of long 
crop diverticula in somite x1x. (Figure 1), and is crowded out in the form of 
one or more loops between the testes (Figure 4); it may even find room for 
itself by crossing into the opposite half of the body. Ultimately it bends for- 
ward again and, narrowing, continues as the muscular and glandular ejaculatory 
duct (Figure 4, dt. ej7.). The ejaculatory duct, as it runs forward, passes out- 
side of the inner row of dorso-ventral muscles at about the point where the 
collecting portion of the vas deferens enters the median lacuna. It then runs 
forward into somite xI., where, turning sharply back again, it expands into 
a thick-walled “terminal horn,” which, uniting with the terminal horn of 
the other half of the body, opens to the outside by the mid-ventral male genital 
pore (po. g, Figure 4). The special function of the ejaculatory duct and par- 
ticularly of its terminal horn, Whitman (’91) has shown to be the formation 
and extrusion of the spermatophore. 

In the early spring, as the water in the ponds begins to grow warmer, the 
seminal vesicles are seen to be gorged with sperm, and the formation of sper- 
matophores takes place rapidly. These the animals attach to one another’s 
backs. Whitman (’91) has shown that in the case of G. parasitica (‘‘ Clépsine 
plana”) the contents of the spermatophore pass through the integument into 
the body cavity, and that impregnation probably occurs while the egg is still in 
the ovary. A similar process doubtless occurs in the case of G. stagnalis. 

After the period of active spermatophore formation has passed, — it ordinarily 
lasts but a few days or weeks, depending upon the rapidity with which the 
temperature of the water rises, — the vasa deferentia are seen to be greatly re- 
duced in size and the testes quite inconspicuous, though in the fall they were 
the most conspicuous organ in the entire body. 

The ovaries (Figure 4, oa.) are a pair of simple sacs extending back from 
the female genital pore in the median lacuna, usually ventral and lateral to the 
digestive tube. They are attached more or less loosely by mesenterial strands 
of connective tissue to those portions of the vasa deferentia which lie in the 
median lacuna. This connection, however, is so slight that when crowded for 
room an ovary may extend out in loops between the testes, or across into the 
opposite half of the body, just as the vasa deferentia do. The size of the 
ovaries depends upon the state of maturity of the contained ova. They are 


26 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


largest in the early spring immediately before the eggs are laid, when they 
often extend the whole length of the genital region and are looped or folded, 
as are the seminal vesicles ; they are smallest immediately after the egg-laying. 
A mean between these two extreme conditions is shown in Figure 4. 

The time of egg-laying, as well as of spermatophore formation, depends upon 
the warming of the water in the spring. One can hasten both processes by 
bringing the animals for a few days into a heated room. Around Cambridge 
the eggs are laid mostly in the months of April and May. Small-sized indi- 
viduals, however, may come to maturity later in the season, even as late as 
September. 

The eggs are pink in color and about 0.3 mm. in diameter. They are 
attached to the under surface of the body in groups of two to eight eggs each. 
Each group is enclosed in a separate, delicate, transparent sac, which adheres 
to the under surface of the body. The sacs are arranged in two longitudinal 
rows close together, one on either side of the median plane of the body. The 
more posteriorly placed sacs usually contain more eggs than those farther 
forward. 

I have not observed the process of egg-laying, but believe that the eggs of a 
single sac are laid at about the same time, that they are then crowded back as 
far as possible under the body, and that there is poured over them a secretion 
from the clitellar glands which hardens into the delicate wali of the sac. After 
a period of rest, during which the body is closely applied to the group of eggs 
so that its sac becomes fastened to the body, another group of eggs is laid, and 
so on until all the mature eggs have been expelled from the ovary. The cli- 
tellar glands are deep-seated, unicellular epidermal glands opening on the 
ventral surface in the vicinity of the female genital pore. They can be 
demonstrated by methylen-blue staining. 

Animals which are kept in aquaria lay their eggs at night, and always com- 
plete the process in a single night, so that all the eggs borne by an individual 
are in about the same stage of development at one time. 

I think it probable that the egg sacs are arranged in the order laid, from 
behind forward, for in one of the most anterior sacs a single egg is occasionally 
found, but never in one of the more posterior sacs have I abeceed so small a 
number. The number of eggs laid by an individual depends. upon its size. 
An animal thirteen mm. long (when fully extended) was found to have laid 
sixteen eggs; another twenty-six mm. long was found carrying forty-five eggs. 
The average number for nine individuals examined at one time was thirty-one. 

The usual number of egg sacs formed is six or eight; in one case examined 
it was ten. The average number of eggs found in a sac is about four ; for the 
most anterior pair of sacs it is three. 


e. DiGESTIVE- TRACT. 


The position of the mouth (or, Figures 3, 7), except when the body is much 
contracted, is anterior to the eyes, in the third somite (ring 2). 
It leads dorsally into the pharyngeal sac (sac. phy., Figure 7), which con- 


CASTLE: NORTH AMERICAN RHYNCHOBDELLID&. 27 
tinues backward through the brain mass, ending in somite xu. (Figure 1). 
Within the pharyngeal sac lies the proboscis (pr’b., Figure 1), which, in a state 
of rest, usually extends from a point just behind the brain back into somite 
x1I., where the ducts of the salivary glands enter its walls. These glands 
(gl. sal., Figure 1) are a conspicuous feature of a Glossiphonia differentially 
stained. They are always unicellular, and represent the largest cells found in 
the body except certain nephridial cells and eggs approaching maturity. The 
salivary gland cells have a great avidity for stains. They number in this 
species thirty or more in each half of the body, and are found scattered through 
about three somites (x1.-xtv.). The largest gland cells are those most remote 
from the base of the proboscis. Each cell has a separate slender duct leading 
into the wall of the proboscis and opening into the lumen of that organ at 
some point along its length. 

A short slender esophagus (@., Figure 1), ordinarily lying entirely within 
somite XIII., connects the base of the proboscis with the crop (vglv., Figure 1). 
This readily distensible part of the digestive tract extends over six somites 
(xtv.-x1x., Figure 1). Under ordinary circumstances it has but a singie pair 
of lateral diverticula ; these arise in somite xIx. and extend backward, usually 
ending in somite xxi. After a full meal, however, short lateral diverticula 
may sometimes be seen also in the five more anterior somites (XIV.-XVIII.), 
but this condition appears always to be a transient one. 

The stomach (ga., Figure 1) begins in somite xx. and ends in somite XXIII. 
It bears four pairs of persistent lateral diverticula doubtless originally seg- 
mental in origin, but now crowded within the limits of about three somites. 
The first two pairs of stomach diverticula are directed forward, the last pair 
backward ; the third pair lies about at right angles to the long axis of the body. 

The terminal part of the digestive tract, the intestine (in., Figure 1), is a 
gradually narrowing tube; it includes one or two proximal chambers separated 
from the following part by constrictions. 

The anus is dorsal in position, as in all other leeches, and lies within or just 
behind somite xxvil. (Figure A, page 32; Figure 34, Plate 8). Comparison 
with other species, in which the reduction of somites is less extensive, shows 
that primitively the anus lay behind somite xxvil. 


Jj. NEPHRIDIA. 


The nephridia number at least sixteen pairs, possibly seventeen pairs. The 
nephropores (nph’po., Figure 4) lie on the ventral surface of the body, somewhat 
nearer the margin than the median plane, and almost exactly in the middle of 
their respective rings. The nephropores are always found in this genus on the 
middle ring of a somite. I have found them in sections of G. stagnalis in 
somites VIII.-XXIV., with the single exception of somite x11. (ring 28). The 
strong development of the salivary glands in this region may account for the 
possible disappearance of the pair of nephridia which we should expect to 
find here. 


28 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


g. NERVOUS SYSTEM. 


The central nervous system, as in other leeches, consists in the middle part 
of the body of a ventral ganglionic chain of twenty-one distinct ganglia meta- 
merically arranged and joined by paired connectives. Forming an extension 
of this ganglionic chain at either end of the body, one finds a nervous mass 
representing several primitively distinct gangha more or less intimately fused 
together. In the central part of the body the ordinary position of the nerve 
ganglion is in the middle ring of its somite (Figure 4, somites XII.—XVIII.). 
Toward either end of the body, however, there is a slight, but increasing, 
centripetal displacement of the ganglia, just as is frequently the case in the 
central nervous system of Arthropoda. This displacement may amount to as 
much as two-thirds of a somite, or in extreme cases an entire somite. Thus 
we see in Figure 4 that the ganglion of somite vir. lies in the first ring of 
somite VIII, a displacement of two rings; in somites vi1L—x1. the displace- 
ment is only a single ring. About the same amount of displacement occurs in 
somites XIX.-XXII.; In somites XXIII. and XXIV. it amounts to about two 
rings ; and in somites XXV.-XXVII. it is still greater. The positions in which 
the nerve ganglia are shown in Figure 4 are average ones carefully computed 
from the observed positions in five different individuals. The ganglia are 
very constant in position, the extreme variations usually amounting to only a 
fraction of the width of a ring. 

The structure and morphological value of the ganglionic masses at the two 
ends of the body is a subject closely connected with the general question of 
the metamerism of the body. 


h. METAMERISM. 


(1) Number of Somites. 


A number of investigators have discussed the question of how many somites 
are found in the body of a leech, and have reached conclusions varying accord- 
ing as they placed emphasis on one or another of the following criteria: 
(1) The number of external rings ; (2) color markings of rings, or the recur- 
rence of peculiar papillz on certain rings of each somite; (3) metameric sense 
organs; (4) the number of ganglia in the central nervous system as determined 
(a) by a count of the nerve capsules, typically six to a ganglion, or (6) by 
ascertaining the number and peripheral distribution of the nerves arising from 
the ganglia. 

Whitman (’92), making use principally of the criteria named under 3 and 4, 
was the first to obtain an entirely satisfactory answer to the question. He has 
shown that in the central nervous system of ‘* Clepsine hollensis” (which is 
closely related to G. parasitica) there are present thirty-four ganglia, each giving 
off paired nerves. Six of these ganglia are found in the anterior ganglionic 
mass which encircles the pharyngeal sac; seven are found in the posterior 


CASTLE: NORTH AMERICAN RHYNCHOBDELLIDA. 29 


ganglionic mass which lies in the posterior sucker and supplies it with nerves ; 
these, added to the twenty-one distinct ganglia found in the central part of the 
body, bring the total up to thirty-four. An examination of the sense organs 
connected with these ganglia, and situated typically on the middle ring (first, 
Whitman) of each somite, yields corroborative evidence that the number of 
somites represented in the body is thirty-four. 

Bristol (99) subsequently made a similar study of the metamerism of 
Nephelis lateralis, his conclusions being for the Gnathobdellide entirely in 
harmony with those ef Whitman for the Rhynchobdellide. 

Oka (94), however, has cast doubt upon the general applicability of Whit- 
man’s determination, based as it was on the metamerism of a single species of 
Glossiphonia, by stating that in the several European species which he has 
studied (G. stagnalis, G. complanata, G. concolor, G. heteroclita, G. papillosa, 
G. marginata, and G. tessellata) he finds evidence of only five (not of six) fused 
ganglia in the brain. Moreover, in recent systematic papers, such as those of 
Blanchard (’94) and Moore (’99), we find the body of the leech still analyzed 
and described as consisting of twenty-six preanal somites, instead of twenty- 
seven, the number found in that portion of the body by Whitman (’92) 
and Bristol (99), and still earlier, though on less satisfactory evidence, by 
Apathy (88). 

Accordingly, I have thought it worth while to examine into this matter 
rather carefully in the case of the species studied by me. 

I may say at once that my results, in the case of all six species studied, are 
in complete accord with those of Whitman (’92), so far as the number of meta- 
meres is concerned. In determining the kmits of the somite, I have arrived at 
conclusions differing from those of my predecessors, as will presently appear 
(p. 31 ff.). 

a. Structure of a Typical Ganglion. — A typical ganglion from the middle 
of the body has its ganglion cells arranged in six groups enclosed in capsules of 
connective tissue. Four of these capsules are lateral in position, two on each 
side of the ganglion ; the other two occupy a mid ventral position, one in the 
anterior, the other in the posterior part of the ganglion. (See the ganglion of 
somite xxvI. in Figure 9, Plate 3.) Three nerves are given off close together 
from either side of the ganglion, and are distributed to the three successive rings 
of one and the same somite, as I have elsewhere (Castle, 1900) pointed out. 

If, then, we can determine exactly how many such ganglia are present in the 
eentral nervous system of a leech, we shall be in a position to say how many 
somites enter into the composition of its body. 

In the middle part of the body, as already stated, twenty-one distinct ganglia 
of the sort just described can easily be recognized. To determine how many 
are present toward either end of the body, where more or less fusion of ganglia 
has taken place, is a matter of more difficulty. 

8. Fused Ganglia. — Figure 9 (Plate 3) shows a dorsal view of the poste- 
rior part of the central nervous system of G. stagnalis, obtained by reconstruc- 
tion from a series of frontal sections. The last two distinct ganglia, those of 


30 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


somites XXVI. and XXVII., are shown, followéd by the nerve mass of the poste- 
rior sucker, made up of seven fused ganglia. In it seven pairs of lateral 
capsules appear on either side, a segmental nerve root being closely connected 
* with each pair (XXvII.-xxxIv.). The more posterior of the lateral capsules 
has in the case of each pair been displaced outward and downward (ventrad) 
and been reduced in size. The position of the seven pairs of ventral capsules 
is indicated by dotted outlines, the numeral denoting the somite to which each 
capsule belongs. In the first and last of the fused ganglia of this region, the 
ventral capsules occupy their typical tandem position (as in ganglion 26); in 
the case of the intervening ganglia (29-33), we find a more or less complete 
displacement of the ventral capsules to a side-by-side position. A similar dis- 
placement occurs in ganglion 27, which lies close back against the septum which 
divides the lacunar space of the posterior sucker from that in which the more 
anterior portions of the central nervous system lie. The same mechanical 
cause, crowding in an antero-posterior direction, explains both phenomena of 
displacement. 

The evidence presented in Figure 9 leaves no room for doubt that seven 
primitive ganglia are found in the nerve mass of the posterior sucker in this 
species. Determination of the number of ganglia represented in the brain mass 
is not quite so easy, but the evidence is likewise convincing. The brain (6., 
Figures 4, 7) forms a ring of nervous substance situated commonly in the last 
ring of somite vi. and the first two rings of somite vi. It surrounds the 
thin-walled pharyngeal sac (sac. phy., Figure 1), there being in leeches no 
recognizable separation into supra- and sub-cesophageal ganglia. 

A lateral view of the brain and the metameric nerves given off from it is 
shown in Figure 8; a view of its dorsal surface in Figure 12. Figure 10 
shows the arrangement of the capsules on its ventral surface. An examination 
of Figures 8 and 10 shows that the capsules (6, 6) of the last brain ganglion 
have quite their typical arrangement. A triple segmental nerve (vI., Figure 8) 
emerges from under a pair of lateral capsules, while below a pair of ventral 
capsules are arranged in the usual tandem order (6, 6, Figures 8, 10).2 

Ganglia 3-5 likewise present no’special difficulties, their lateral capsules 
being present in pairs with nerve roots attached (3,3- 4, 4; 5, 5, Figure 8). 


1] have been unable to determine to what extent in the reduced somites at 
the two ends of the body the original triple nature of the segmental nerves per- 
sists. The nerve of the last brain ganglion is certainly triple (v1., Figure 8). as 
we should expect from the fact that somite vr. consists of three distinct rings 
(Figures 4,7). Most of the nerves anterior to this one, perhaps all, are either 
double or triple, but as I have been unable to determine accurately which con- 
dition exists in some of them, I represent the nerve as undivided in the case of the 
first five somites (Figure 8). Fora like reason I follow a similar course in repre- 
senting the segmental nerves of the posterior ganglionic mass (Figure 9). I think 
that all of these nerves are made up of at least two distinct bundles of fibres ; 
whether the small third nerve is also present as a distinct element in any or all of 
them, I am unable at present to say. 


CASTLE: NORTH AMERICAN RHYNCHOBDELLID. oi 


Their ventral capsules show the following modification in arrangement ; 
they have been displaced from the typical tandem position to a side-by-side 
position (Figures 8, 10; compare Figure 9, somites XXIX.—XxxXIII.). 

The lateral capsules of ganglion No, 2 are found dorsal to the pharyngeal sac 
(2, 2, Figures 8, 12). They seem to have been displaced backward to a po- 
sition somewhat posterior to the lateral capsules of ganglion No. 3 by a migration 
in that direction of the supra-csophageal commissure (Figure 8 ; compare 
Figures 11, 21). The commissure in this species is normally thrust back of 
the position in which it is shown in Figure 8, so that it lies about over the 
lateral capsules of ganglion No. 5. The animal whose brain is represented in 
Figure 8 was curved ventrad so that the commissure was thrust forward of its 
usual position and the row of lateral capsules below it was straightened out 
a little. The position of the ventral capsules of ganglion No. 2 is shown in 
Figures 8 and 10; the nerve root (11., Figure 8) arises at the anterior end of 
the brain just ventral to nerve root I. 

The ganglionic capsules of neuromere No. 1 all lie dorsal to the pharyngeal 
sac and anterior to the supra-cesophageal commissure (Figures 8, 12). I be- 
lieve that the most anterior and ventral of these (1v., Figures 8, 12), which 
lies closely attached to nerve root I. in each half of the body, is homologous 
with a ventral capsule of one of the succeeding ganglia, Capsule rv. extends 
out lateral to, sometimes even ventral to, nerve root I., so that its end may 
appear in sections between nerve roots I. and It. 

Oka (94) states that he finds in the brain of “Clepsine” (Glossiphonia) 
always thirty nerve capsules, and he accordingly regards it as equivalent to 
five fused ganglia and no more. Since G. stagnalis was one of the species 
studied by him, I am unable to understand how he can have reached such a 
conclusion, unless he has overlooked altogether the capsules of somite 1. which 
lie anterior to the supra-cesophageal commissure. 

Both the number and arrangement of the nerve capsules, and the number and 
position of the nerve roots, show clearly that in G. stagnalis stx fused ganglia are 
represented in the bran, and that in the entire body THIRTY-FOUR somites are 
represented. 


(2) Somite Limits. 


It remains to explain the grounds on which the limits of the somites have 
been placed by me as indicated in Figure 4. Whitman (’85) pointed out 
many years ago that a certain ring (the first, according to his account) of each 
typical somite in the body of a leech is more richly supplied with sensory 
organs (“‘sensille ”) than any other ring of the somite. In many species of 
Glossiphonia special color markings or papille are also found on the sensory 
ring. Color markings, however, are wanting in G. stagnalis, and the sen- 
sillxe are not sufficiently conspicuous in the living animal to make identification 
of the sensory rings at all certain. But a carmine stain of the proper intensity 
renders identification of the sensory rings quite easy by giving them, especially 
along the margins of the body, a somewhat darker color. Observing this fact, 

VOL. XXXVI. — NO. 2. 2 


32 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


I was first enabled to determine as sensory the rings indicated by Arabic 
numerals in the right half of Figure 4 ; further study revealed the presence of , 
marginal sensille in the positions indicated in Figure 3. 

The metamerically repeated sensory annuli were thus positively identified 
throughout the greater part of the body. It remained merely to mark off the 
somite limits between successive sensory annuli. This I at first did after the 
usage of Whitman (’85, 92) and practically all others since the time of Gra- 
tiolet (62), considering the sensory ring as occurring at the anterior end of 
ats somite. 

I found, however, that a consistent following of this practice would, toward 
either end of the body, place the somite limits in the middle of a ring instead 
of between rings, the position in which somite boundaries fall in other regions 
of the body. See Figure A, xXv’., xxvr’,, etc. 


XXVIL? <8. 


Fieure A.— G. stagnalis. Dorsal view of posterior part of body, showing mar- 
ginal sensilla. Somite limits are indicated correctly at the right of the figure 
(xxIv. to xxvit.); at the left of the figure (xx111’. to xxvm’.) they are shown 
as they have been commonly but incorrectly placed. 


This led me to inquire whether the sensory ring really is the anterior ring 
of its somite. The results of this inquiry have been published elsewhere 
(Castle, 1900), so that only one or two of the more important conclusions 
need be restated here. One of these, already suggested in part on page 29, 
is the following : — 

Somite limits coincide with neuromeric limits ; consequently in Glossiphonia the 
sensory ring is the middle, not the anterior ring of the somite. 


CASTLE: NORTH AMERICAN RHYNCHOBDELLID. 303 


This point being established, the somite limits must be marked off, in the 
regions where unabbreviated somites occur, as in Figure 4, vI.-xxrv. 

I have further shown, in the publication already cited, that in Glossiphonia 
somite abbreviation! is accomplished by a series of steps which follow one 
another in regular sequence. First, a union takes place between the sensory 
ring and the ring which precedes it; secondly, the ring which follows the sen- 
sory ring is reduced in size; finally, it too fuses with the sensory ring, the 
entire somite being then represented by a single external ring. 

If, as is not improbable, some of the “ abbreviated” somites are really in 
arrested. stages of development from the one-ringed to the three-ringed con- 
dition (as suggested in the case of Microbdella by Moore, 1900), the order of 
the three steps enumerated should be reversed, in their case, and described in 
the following terms: (1) A distinct narrow ring is separated off at the pos- 
terior end of the uniannulate somite; (2) this newly formed posterior ring 
grows in width ; (3) another new ring is separated off at the anterior end of 
the somite. This produces a three-ringed somite, all three rings ultimately 
attaining an equal width. For convenience in description, however, the pro- 
cess will be uniformly treated as one of abbreviation, as explained on page 22, 
footnote. 

The amount of “abbreviation,” as is well known, becomes greater toward 
either end of the body. 

Bearmg in mind these principles, we find that the least affected of the 
abbreviated somites of G. stagnalis are those which stand nearest to the un- 
abbreviated somites, namely, v. (Figure 3) at the anterior end of the body, 
and xxv. (Figure A) at the posterior end. In the case of each of these, the 
anterior and sensory rings of the somite are united into a single broad ring. 
But in the case of somite v. we find the union occasionally incomplete, as in- 
dicated by the notch (less clearly than it should be) at the upper margin of 
Figure 3, ring 4. 

Somite xxvi. (Figure A; Figure 34, Plate 8) is usually found in the same 
condition of abbreviation as the somites just described. Occasionally, however, 
its posterior ring is narrower or less distinct than that of somite xxv. 

In somites 11. and rv. the process of abbreviation to a single broad ring is 
practically complete, although the narrow posterior ring is in favorable pre- 
parations still recognizable as a distinct element separated from the rest of the 
somite by a shallow transverse furrow (Figure 7, 111., Iv.). 

Somites 1., 11, and xxvii. have each been reduced to a single ring; in 
addition a fusion (sometimes incomplete) has taken place between somites 1. 
and I1., so that they are together represented by the broad ring, 1 (Figure 7). 

Somites XXVII.-XXXIV. are not represented by annuli on the surface of the 
body ; they form collectively the posterior sucker. 


1 As to the sense in which this term is used, see p. 22, footnote. 


34 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


2. Glossiphonia fusca sp. nov. 


Plate 4. 
a. Hapitat, Form, Siz, Conor. 


This species is rather closely related structurally to G. stagnalis, with which 
I have found it associated in the vicinity of Cambridge, Mass., and Trenton, 
New Jersey. It is of about the same size as G. stagnalis, but is broader in 
proportion to its length (Figure 13, Plate 4). In its movements it is some- 
what more sluggish than that species and does not stretch itself to so great 
a length. 

Length of largest individuals, fully extended, 20 mm.; at rest, 9 mm. 

Greatest width, when fully extended, 2.5 mm.; at rest, 4 mm. 

Color, a coffee-brown above, somewhat lighter below. The general brown 
coloration is due to the presence in the superficial layers of the body of slender, 
branched, thread-like pigment cells bearing numerous knot-Jike swellings and 
filled with a dark-brown pigment. Such pigment cells are clearly homologous 
with the pigment cells found in a superficial position in the body of G. stag- 
nalis, — Graf’s *‘ excretophores.” They are much more abundant on the dorsal 
than on the ventral surface. On the former they appear in greatest numbers 
in a median dark band about as wide as two or three body rings; but they are 
entirely wanting anterior to the eyes and in the following regions, which 
therefore appear as clear, transparent areas : — 

1. A transverse row of circular spots found on the sensory ring of each 
somite. These spots are about the width of a ring in diameter. Their maxi- 
mum number is seven, but it is a rare occurrence to find all seven present in 
a single somite. Each spot occupies a definite position on its ring, so that 
those of successive somites form seven longitudinal rows, three in each half of 
the body and one median in position. The paired rows may be designated as 
marginal, intermediate, and paramedian, for they occupy positions which cor- 
respond closely with those of the rows of dorsal papille so designated in the 
case of G. parasitica (Plate 2, Figure 6). 

The paramedian rows of clear spots are more constant in occurrence than any 
of the others ; they can usually be found on somites v.-xxvi. The intermediate 
and marginal rows usually begin about in the region of the genital pores and 
continue with increasing distinctness back to the anus, The median row 
is less well developed than any of the others. It is represented by an oc- 
casional clear spot in the region posterior to the genital pores and anterior to 
somite XXII. 

2. In the region of somites xx1t—xxvi., the median row of clear spots is 
suddenly replaced by a continuous clear band about as wide as one of the spots. 
Along the margins of this clear band, the pigment is unusually abundant, 
which fact adds by contrast to the conspicuousness of the median band. 

3. The margin of the posterior sucker, where it projects beyond the outline 
of the body as seen in dorsal view, usually bears eight or ten triangular or 


CASTLE: NORTH AMERICAN RHYNCHOBDELLID&. 35 


rounded clear spots of approximately the same form and position as the yellow 
pigment spots found on the posterior sucker of G. parasitica (see stippling in 
Figure 6). 

4, The sensory ring of each of the somites in the neck region — somite vy. 
and a few of the following — is occasionally distinguished by an uninterrupted, 
but narrow, clear band, which runs entirely across it from one side of the body 
to the other, occupying about its middle third. 

The conspicuousness of the unpigmented areas just described, except that 
mentioned under (4), is increased by the presence in the centre of each of 
a group of peculiar reserve-food cells, which lie quite near the surface of 
the body. 

The ordinary reserve-food cells of this species agree in practically every par- 
ticular of structure and distribution with those of G. stagnalis. They are large 
rounded cells, sometimes attaining a diameter of eighty mikra or more. The 
granules within their cytoplasm attain a diameter of six or seven mikra. The 
color of these cells by reflected light is a pale orange; by transmitted light, 
they are semi-transparent, of a leaden gray color. They are distributed ir- 
regularly through the middle and posterior portions of the body, being situated 
in its deeper parts. 

The special form of reserve-food cell, which is found in the segmental clear 
spots already described, differs in respect both to size and to color from the ordi- 
nary reserve-food cell. It is considerably smaller, — forty to fifty mikra being 
the maximum diameter observed, — and its contained granules are likewise 
smaller, though more numerous. Its color by reflected light is a bright lemon 
yellow ; by transmitted light it is brown. Finally this variety of reserve-food 
cell is invariably situated quite near the surface of the body. The appearance 
of a group of these cells as seen under a moderately high power of the micro- 
scope is shown imperfectly in Figure 17 (Plate 4). 

The ventral surface of the body is pigmented in very much the same fashion 
as the dorsal, but less heavily. There is, however, this difference in the dis- 
tribution of the superficial brown pigment : on the ventral surface a pair of 
narrow, paramedian, pigmented lines can be recognized, one in each half of 
the body, in about the position of those found both dorsally and ventrally in 
G. elegans (Figure 30, Plate 7). On the dorsal surface, on the other hand, 
the most heavily pigmented region is a broad median band (p. 34). 

Segmental clear spots are found on the sensory rings on the ventral surface 
also, and these are arranged in paramedian, intermediate, or marginal rows; 
but the spots are much less conspicuous than on the dorsal surface, and the 
lemon-yellow reserve-food cells are less often found in their centres. 

Comparing the coloration of this species with that of G. stagnalis, we may 
say that the histological elements which produce the coloration are very similar 
in the two, but the distribution of these elements is such as to produce in G. 
fusca a distinct color pattern (longitudinal striations and segmental clear spots), 
a feature entirely wanting in G. stagnalis. 


36 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


6. Rives, Somires, Eyes, SucKERs. 


External rings, not quite so distinct as in G. stagnalis ; skin, slightly rougher 
owing to the stronger development of Bayer’s (96) sense organs. Number of 
preanal rings, seventy (Figure 13, Plate 4). 

Somites V.-XXIV. are triannulate, but the two anterior rings of v. are united 
ventrally (Figure 15). 

Somites I. and 1. are included in a single broad ring, which, just as in G. 
stagnalis, is sometimes subdivided by a shallow transverse furrow (Figure 14) 
marking the boundary between the two incompletely fused somites. 

Somites IIl., Iv., XXV. and xxvi. (Figures 13-16) are biannulate. In each 
case the broader, anterior ring bears the sensilla and corresponds to rings 1 and 
2 of triannulate somites (compare somites Iv. and v. of Figure 15). 

Somite XXVII. is a single broad ring (70, Figure 13) which lies just anterior 
to the anus, not crowded back of it, as in stagnalis (Figure 34, Plate 8). 

The principal differences in somite composition between fusca and stagnalis 
occur in the head region, in somites 111.—v. These somites are less abbreviated 
(or more fully elaborated) in fusca than in stagnalis, hence the greater number 
of preanal rings in the former (seventy) as compared with the latter (sixty- 
seven). 

Eyes, two, large and distinct, situated in rings 3 and 4 (Figures 14-16). 
The sensory elements of each eye, as in G. stagnalis, are contained in a pig- 
ment cup which is open only on its anterior, lateral surface, where the nerve 
fibres make their exit (Figures 14, 16). 

Oral sucker, as in all species of Glossiphonia, included within the first four 
somites (Figures 14, 15). 

Posterior sucker of about the same dimensions as in G. stagnalis, slightly 
longer than broad. 


c. REPRODUCTIVE ORGANS. 


Male genital pore (po. @, Figure 13), between the first and second rings of 
somite xII. (rings 27 and 28). 

Female genital pore (po. 9, Figure 13), between the second and third rings 
of somite XII. (rings 28 and 29). 

Testes (te., Figure 13), six pairs situated intersegmentally in somites 
XIII. XVIII. 

XIve) Suen 

The ovaries have the usual form and position of these structures in other 
species, being found ventrally in the median lacuna. 

Eggs are laid a month or six weeks later than by G. stagnalis (June 12, 
1898, Cambridge, Mass.). In color they resemble those of G. stagnalis closely, 
being of a light pink or flesh color. As in G. stagnalis, the eggs are attached 
to the under side of the body posterior to the genital pores, within a number 
of delicate sacs arranged in two parallel rows, close together, one on each side 
of the median plane. The number of sacs is most often six, but a seventh sac 


CASTLE: NORTH AMERICAN RHYNCHOBDELLIDA. oT 


was observed in one case. The number of eggs in a sac, as well as the total 
number of eggs laid by an individual, is greater in this species than in G. stag- 
nalis. The following figures will indicate the number of eggs borne by four 
good-sized individuals, which laid eggs in the laboratory in June, 1898. The 
vertical line represents the median plane of the body; the positions of the 
numerals show how the sacs were placed with reference to one another and to 
the median plane of the body ; the numerals themselves indicate how many 
eggs were in each sac. Anterior is toward the top of the page, and the right 
side of the body toward the left of the page, the animals having been observed 
in ventral view. 


Inpivipuat I. Inpivipuat IL. 
da. a. 
16 | 17 11 6 
T 16. 20 ye ie ile 13 l. 
22 | 13 1g | 14 
Pp: p- 
Total 54 + 50 = 104 444 33=77 
Inpivipuav IIL. INDIVIDUAL IV. 
a. 
a. 5 
2] 13 16 | 14 
iF 18 20 l. ite 21 “19 ie 
19 | 18 17 | 13 
ie Pp: 
39 + 51 = 90 54 + 51 = 105 


Average number of eggs in a sac in above cases, 15 (as against 4 in G. stag- 
nalis); average number of eggs borne by an individual, 94 (as against about 30 
in the case of G. stagnalis). 

It will be noticed that one of the anterior sacs often contains a relatively 
small number of eggs (as noticed in the case of G. stagnalis also), suggesting 
that it served to finish off the egg-laying, the sacs being arranged in the order 
in which they were formed, from behind forward. 


d. DiGESTIVE TRACT. 


The mouth is situated anterior to the eyes, well forward in the anterior half 
of the oral sucker (Figures 14,15). From here the thin-walled pharyngeal sac 
(sac. phy., Figure 13) leads back to the base of the proboscis in somite XII., just 
behind the male genital pore. When the animal is at rest the proboscis (pr’b., 
Figure 13) usually extends through the four somites between the brain and 


38 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 


the male genital] pore (VIII.-xI.) into somite xII., where it receives the ducts 
of the salivary glands, a bundle from either side of the body. 

The salivary glands themselves are very large in this species and are dis- 
tributed in the marginal part of the body through somites xI.—Xxvil., or, in 
exceptional cases, even a somite farther in one direction or the other. 

The short wsophagus (@., Figure 13) extends from the base of the proboscis 
through somite xI1I. to the beginning of the crop in somite XIV. 

The crop («glv., Figure 13) extends over the six somites XIV.—XIX., giving 
off in the middle of each a pair of conspicuous lateral diverticula. These are 
always evident whether the crop contains food or not, a condition very different 
from that which exists in G. stagnalis. The last pair of crop diverticula (those 
of somite XIx.) are very long but simple, as in G. stagnalis, without secondary 
lateral diverticula. They extend back over the entire stomach region, usually 
ending in somite XXIII. 

The stomach (ga., Figure 13), which is separated from the crop by a valve- 
like constriction, bears four pairs of lateral diverticula doubtless originally 
metameric in arrangement, but now arising within the limits of somites 
XX.—XXII. 

The intestine (in., Figure 13) leads from the stomach back to the anus, which 
is situated dorsally just behind somite xxvII., as in other species of Glossi- 
phonia. The intestine includes anteriorly two rather spacious chambers, the 
first of which bears a pair of small ear-like diverticula from its anterior lateral 
borders. Behind these chambers comes a simple tubular part terminating at 
the anus. 

To sum up, the particulars in which the digestive tract of G. fusca differs con- 
spicuously from that of G. stagnalis are (1) the shorter proboscis and larger 
cesophagus; (2) the larger salivary glands, distributed through a greater num- 
ber of somites; (3) the persistent character of the first five pairs of crop diver- 
ticula; (4) the distinctly chambered condition of the intestine, and the pair of 
diverticula borne by its first chamber. 

Nephropores are found on the sensory ring of each of the somites VIII.—XXTVv., 
with the possible exception of x1iI., where, as in stagnalis, the nephridia are 
much reduced, if not wholly wanting, —a fact accounted for by the strong 
development of the salivary glands and genital ducts in that region. The 
nephropore lies usually a little anterior to the middle of the ring on which it 
is found. 


e. Nervous SYSTEM. 


A ventral view of the brain is shown in Figure 18, a dorsal view of that part 
of it which lies above the pharyngeal sac is shown in Figure 16, the position 
of the ventral part being indicated by a dotted line ; the outline of the brain 


1 The animal shown in Figure 13 was a small one, and the salivary-gland cells 
are proportionally a little larger than they would be in the average, full-grown 
animal. 


CASTLE: NORTH AMERICAN RHYNCHOBDELLID, 39 


as seen in a lateral view is shown in Figure 14, cb. It lies for the most part 
in somites vit. and v1. This is about a somite posterior to the usual position 
of the brain in G. stagnalis (Figures 4, 7). 

The number of fused ganglia represented in the brain is, as in G. stagnalis, 
six, and the nerve capsules have the same general arrangement as in that 
species. The yentral capsules of neuromeres I1.—v. are placed side by side, 
while those of neuromere VI. lie one behind the other (Figure 18 ; compare 
Figure 10, Plate 3). The six capsules of neuromere I. are situated well dorsal, 
as in G. stagnalis, and the supra-cesophageal connective is pushed back nearly 
over the middle of the entire brain mass (Figures 14, 16). The lateral cap- 
sules of neuromere II. are shown in the dorsal view (Figure 16) ; those of neu- 
romeres III.-VI., in the ventral view (Figure 18). 

In Figure 14, which represents a parasagittal section, is shown the position 
of the paramedian sensille of the head somites, certain of which also appear 
in Figure 15. These indicate clearly the sensory rings of the somites in that 
region, and so aid in the determination of the external limits of the somites, 
The eye is clearly derived from one of the segmental organs of somite I. 
(ring 2), as the position of its nerve indicates. This view is confirmed by a 
comparison with the conditions existing in G. heteroclita and G. elegans. 


8. Glossiphonia elongata sp. nov. 


Plate 6. 
a. Hasitat, Form, Size, Cotor. 


This leech first came to my notice in September, 1898. While collecting 
G. stagnalis from Spy Pond, near Cambridge, I found three or four leeches 
which, although of about the same size as stagnalis and occurring in similar 
situations, at once attracted my attention because of their more slender bodies 
and the peculiarities of their movements. These animals were carefully pre- 
served, and diligent search was made the following spring for more. This 
search, however, was fruitless ; but in September, 1899, I was fortunate enough 
to find quite a number of individuals in a pool near Fresh Pond, Cambridge, 
some of which I have since kept alive in aquaria for several months. 

The body is less flattened dorso-ventrally in this species than in any other 
Glossiphonia known to me, being sub-cylindrical in cross-section. It is ex- 
tremely slender, even when contracted, and both head and acetabulum are 
small (Figure 27, Plate 6). This species does not roll itself into a ball, as 
other species do, when disturbed. Instead, it writhes about or twists itself 
into knots like an earthworm. In aquaria it moves little from place to place, 
but, attached by its weak posterior sucker, extends its snake-like body searching 
hither and thither as for a place of concealment, or, losing its attachment, seems 
unable to regain it and writhes helplessly like an earthworm on a smooth 
surface. 

The largest individuals which I have examined measure as follows : — 


40 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


Length, fully extended, 25 mm.; partially contracted (as in Figure 27), 
about 10 mm, 

Width, fully extended, less than 1 mm.; partially contracted (as in Figure 
27), about 1.5 mm. 

Color. — The anterior and marginal parts of the body are very clear and 
transparent. The rest of the body is usually of a pale yellowish-white color 
when the animals are first collected, but changes to a rusty yellow or pale 
orange color if they are kept in well-lighted aquaria for a few days. The color 
is due to the presence in the deeper parts of the body of rounded reserve-food 
cells, similar to those described as occurring in G. stagnalis. Apparently the 
nature of the granules in the reserve-food cells changes under the influence of 
daylight, so that by reflected light they appear pale orange instead of yellowish- 
white, the color which they have when first collected. 

Superficial pigment cells of the branched type, described as occurring in G. 
stagnalis and other species, appear to be entirely wanting in G. elongata. 

Fat cells occur in abundance in the deeper parts of the body, the contained 
oil drops being perfectly clear and transparent, as in G. stagnalis and G. fusca. 


6. Rinxes, Somites, Eyes, Suckers. 


The skin is very smooth and entirely free from papille. 

External rings, broad and smooth, usually indistinct in the head region 
(somites I.-Iv., Figure 23). Number of rings, 62 between oral sucker and anus 
(somites V.—XXVII.). 

Notwithstanding the indistinctness of the rings in the head region, favorable 
preparations, like that represented in Figure 6, show that the composition of 
somites I.-Iv. is practically the same in this species as in G. heteroclita (Plate 5) 
and G. fusca (Plate 4). Somites I. and I. are uniannulate; somites 111. and 
tv. biannulate, the anterior rings being broader and corresponding to rings 1 and 
2 of a typical somite taken together. 

Somite v. is likewise biannulate in this species, just as in G. stagnalis 
(Figure B; compare Plate 1, Figure 3) ; in all the other species with which 
this paper deals, somite v. is triannulate. 

Somites v1.-xx1v. (Figure 27) are triannulate, as in all other known species 
of this genus. Somites xxvy.-xxvil. are reduced each to a single ring, a con- 
dition found in the other species described only in the case of somite XXvVIZ., 
somite xxv. being always biannulate, and somite xxv. usually so. 

Eyes, two, situated about as in G. stagnalis, just posterior to the mouth, 
between somites 11. and Iv. (Figure 23). The eyes are separated from each 
other by a considerable space, as in G. stagnalis (Plate 2, Figure 4) and G. fusca 
(Plate 4, Figure 16). The pigment associated with them is usually small in 
amount; often it is wanting altogether. 

The oral sucker, as in the other species described, lies within the limits of 
somites 1.-Iv. The mouth lies about in its centre (Figure 23, Plate 6; Figure B). 
The posterior sucker (act., Figures 24, 27) is extremely small and weak. In 


CASTLE: NORTH AMERICAN RHYNCHOBDELLIDZ. 4] 


position it may be described as terminal rather than ventral (the position 
which it occupies in other species). 


ce. REPRODUCTIVE ORGANS. 


The genital pores have the same position as in G. stagnalis and G. fusca; the 
male (po. ¢, Figure 27), between the first and second rings of somite x1I., the 
female (po. 2, Figure 27), between the second and third rings of the same 
somite. 


Ficure B.— G. elongata. Ventral view of head end, showing annulation of head 
somites and position of marginal sensillz. 


Testes (te., Figure 27), six pairs placed intersegmentally in somites 
= XL. | XVINT. 
XEVs | XEX 

The ovaries (oa., Figure 27) have the typical structure and position which 
they possess in other species (see p. 25). The eggs and egg-laying of this 
species I have not observed. 


» as regularly in the genus. 


_d. Dicestive TRACT. 


The mouth (or., Figure 23, Figure B) opens about in the middle of the oral 
sucker. The proboscis (pr’b., Figure 27) commonly extends over about four 
somites (vi.-xI.). The salivary glands (gl. sal.) are found chiefly in so- 
mite x1I., though a few may lie in the adjacent somites, x1. and x1. About 
thirty good-sized gland cells are found in either half of the body. In size, 
number, and position the salivary glands of this species resemble those of G. 


42 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


stagnalis more closely than those of any other species (compare Figures 1 
and 27). 

The crop (i’glv., Figure 27), as in G. stagnalis, bears a single pair of diver- 
ticula, which arise in the middle of somite xrx.; but the diverticula are 
shorter in this species than in stagnalis, ending usually in somite xx. (com- 
pare Figures 1 and 27). The stomach (ga.), as in all species of Glossiphonia, 
bears four pairs of lateral diverticula. They arise within the three somites 
xx.-xxu. All are directed slightly forward. The intestine (in.) is a simple 
tube not constricted into distinct chambers proximally as in most species. 
The anus (an., Figure 24) lies just behind somite xxv. 

In the structure of its digestive tract, as well as in the composition of its 
somites, this species shows a more reduced, simpler condition than is found 
in any other species known to me, stagnalis coming nearest to it in these 
particulars. 

e. NERVOUS SYSTEM. 

On account of the transparency of the body the central nervous system can 
be studied with ease in this species, either in the living animal or in whole 
preparations. In the ventral ganglionic chain there are, as in all species of 
Glossiphonia, twenty-one distinct ganglia. These innervate somites VIL.—XxXVII. 
respectively. 

The brain (cb., Figures 23, 27; also Figures 25, 26) represents the fused 
ganglia of the first six somites. The arrangement of its ganglionic capsules 
is the same as in G. stagnalis and G. fusca (Figures 8, 10, 12, 18). The two 
ventral capsules of somite vi. (6, 6, Figure 25) are arranged tandem, those of 
somites I.—-v., side by side. The supra-cesophageal commissure lies well back, 
about over the lateral capsules of somite v. (Figure 26). 


4. Glossiphonia heteroclita Lixyyzvs (1761). 
Plate 5; Plate 8, Figs. 35, 36, 38. 


Hirudo heteroclita Linneus (1761); H. hyalina O. F. Miiller (1774); Clepsine 
hyalina Moquin-Tandon (’26). . 


a. Hasitat, Form, S1ze, Conor. 


This small and transparent leech is found both in Europe and in North 
America. Compared with G. stagnalis and G. fusca, it has a proportionally 
shorter and broader body (Plate 5, Figures 19, 22 ; Plate 8, Figure 38. Com- 
pare Plate 1, Figure 1; Plate 2, Figure 4) ; in its movements, it is less active. 
It is found in ponds and sluggish streams, such as G. stagnalis frequents. 

Length of largest individuals, when extended, 13 mm. ; at rest, 8-9.5 mm. 

7idth, extended, 3 mm.; at rest, 4.25 mm. 

Color. — The body is in general very clear and transparent, like that of a 
jelly-fish, but shows great individual variation in the matter of pigmentation. 

First, it always has more or less of a golden-yellow tint caused by the pres- 


CASTLE: NORTH AMERICAN RHYNCHOBDELLIDA. 43 


ence, in the deeper parts of the body, of large, rounded cells cach containing a 
single yellow oil-drop, which is blackened when treated with osmic acid.2 

Secondly, there are usually present (but this is the variable element in the 
pigmentation) irregularly rounded, oval, or even somewhat branched cells, 
which contain pigment granules either orange, dark-brown, or black in color. 
These cells are found near the dorsal surface of the animal, and often produce 
a conspicuous color pattern by their abundance in certain regions (Figure 38, 
Plate 8). In their finer structure, cells of this variety are rather closely related 
to the deep-seated pigment cells (reserve-food cells) found in G. stagnalis and 
G. fusca; but in respect to position (close to the surface), and occasionally in 
form (irregular or branched), they approach more nearly the superficial pig- 
ment cells (“‘excretophores,” Graf) of the species named. 

The pigmented areas which are often produced in G. heteroclita by the super- 
ficial pigment cells just described are (Figure 38, Plate 8), first, a median dorsal, 
longitudinal band, which, when best developed, extends, with occasional inter- 
ruptions, from about the seventh somite back to the anus. In the anterior 
ring of each somite it often broadens out into a trapezoidal form. Secondly, 
in about the same regions of the body (seventh to twenty-seventh somites), 
the anterior ring of each somite may be marked by a transverse, pigmented 
line, most conspicuous a short distance from the margin of the body, from 
which point it extends inward toward the trapezoidal, broad part of the median 
vitta, but rarely joins it. 

Apathy (’88) has recognized as a distinct variety (striata) animals which 
have the transverse markings just described. It must be said, however, that 
one can find in a lot of animals collected from the same locality all gradations 
between forms with no pigment at all (of the superficial sort) and those having 
a median vitta and well-defined transverse striations. 


b. Rryes, Somrtes, Eyss, SucKERS, ETC. 


The surface of the body is rather smooth, being only slightly rougher than 
that of G. stagnalis. 

External rings, rather inconspicuous, particularly in the head region, where it 
is often difficult to determine their number and limits accurately. 

Number of preanal rings, seventy, counting as a single ring each of the so- 
mites I., II., XXVI., and xxvilI., Figure 19. This number may be increased, 
if one counts subdivisions occasionally visible in some of the rings at the ends 
of the body. 

Somites I. and I1., as just indicated, are commonly uniannulate (Figures 35, 
36, Plate 8); but somite 11. is sometimes subdivided by a transverse furrow (as 
shown in Figure 20, Plate 5). 


1 Fat cells are also found in the deep parts of the body of G. stagnalis, G. fusca, 
and G. elongata, but the contained oil-drops are in those species perfectly clear 
and transparent, so that they do not have the effect of pigment cells, as do the fat 
cells of G. heteroclita. i 


44 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


Somite 111., within the anterior part of which lies the mouth (or., Figure 20), 
is ordinarily biannulate, as are also somites Iv. and xxv. (Figures 19, 35, 36). 
But in the section shown in Figure 20, ring 3, the anterior annulus of somite 
III., appears conspicuously subdivided, a rather unusual condition. On account 
of the obliquity of the section, the first three somites appear in that figure a 
little too long in proportion to their vertical dimensions. The sensilla shown 
in the anterior portion of ring 3 in Figure 20 is probably not one of the seg- 
mental sense-organs, for it is found on the wrong half of ring 3. 

Somites V.-XxIv. are triannulate, as in G. fusca. 

Somites xxvi. and xxvii. (reckoned as uniannulate) usually appear divided 
at the margin only into a broader anterior and a narrower posterior part. 

Compared with the species already described, the somite composition of G. 
heteroclita is about the same as that of G. fusca, somite abbreviation being less 
extensive in these species than in stagnalis and elongata. 

Eyes, usually six, the anterior pair small and generally, though not always, 
close together in ring 5 (Figures 35, 36, Plate 8). Sometimes this pair of 
eyes lies in ring 6; occasionally the pigment of one or both eyes is wanting 
altogether. 

The second and third pairs of eyes are most often found in rings 7 and 8 
respectively, but one pair or the other or both may lie a little anterior or a 
little posterior to the ordinary position (compare Figures 35 and 36). 

The first and second pairs of eyes are directed forward and toward the side ; 
the third pair is directed backward and toward the side (Figures 20, Plate 5; 
Figures 35, 36, Plate 8). The eyes in this species seem to belong to somites 
IlI., IV., and v., respectively (Figure 20); but it is possible (though I think 
hardly probable) that a more careful study of the nerve connections would 
show that in this species, as in G. elegans (Figure 29, Plate 7), they have been 
derived from the sensille of somites 11-1v. If so, the eyes have undergone a 
farther displacement backward in this species than in the case of G. elegans 
(compare Figures 20 and 29). 

Oral sucker, formed by somites 1.-Iv. (Figure 20). 

Mouth (or., Figure 20), in the anterior part of somite 111., usually a little an- 
terior to the first pair of eyes. 

Posterior sucker, as in other species, slightly longer than broad (Figure 19). 


c. REPRODUCTIVE ORGANS. 


Male and female genital ducts open between the first and second rings of 
somite XII. (rings 28 and 29, Figure 19) by a common pore, a condition pecu- 
liar, I believe, to this species. 

Blanchard (94) is certainly in error in describing the position of the genital 
pores as follows: “ Porus genitalis masculus inter annulos 25-26, vulva inter 
annulos 27-28 hians.” 

Testes (te., Figure 19), six pairs placed intersegmentally in somites 
XII. | XVII. 


teers The terminal part of the vas deferens (ejaculatory part) is un- 
Vey eee 


CASTLE: NORTH AMERICAN RHYNCHOBDELLID. 45 


usually stout and thick in this species and runs forward to the middle ring of 
somite XI. before turning sharply backward toward the genital pore (compare 
Figure 19 with Figures 4, 13, 27, and 28). 

The eggs, which in the vicinity of Cambridge are laid in May or June (at 
about the time G. fusca is laying), are whitish in color and are attached 
singly, not in groups as in the other species described, to the under side of the 
body (Figure 22). The eggs are of about the same size as those of G. stagnalis, 
The number laid varies greatly with the size of the individual, the observed 
extremes being eleven and sixty-five. Figure 22 shows in ventral view a large 
individual bearing forty-five eggs, each enclosed in a separate delicate sac 
which serves to attach it to the under side of the body. 


d. Digestive TRACT. 


The mouth has the position most common in the genus, in the anterior part 
of somite 111. (Figure 20). 

The proboscis (pr’b., Figure 19) is long and the esophagus correspondingly 
short. The former ordinarily extends over somites Ix.—x1. and part of xIII., 
and the latter ends in the anterior part of somite xtv., where the crop com- 
mences. 

The salivary glands (gl. sal., Figure 19) are large and distributed often 
through as many as seven or eight somites, usually somites X1I—XVII. 

The crop (Vglv., Figure 19) bears six pairs of strongly developed lateral 
diverticula, a pair arising in the middle of each of the somites xIv.—xIx. 
Some or all of the first five pairs may be bilobed distally, and each of the 
sixth pair, which are very long, and extend back into somite xxut., bears 
about five secondary, lateral diverticula, which come off metamerically in 
somites XIX.—XXIII. 

The stomach (ga., Figure 19), with its four pairs of lateral diverticula, lies 
within somites XIX.—XXII. 

The intestine (in., Figure 19) begins about in somite xx1I. and extends back 
to the anus just behind somite xxviI. Proximally it consists of one or two 
chambers limited by valve-like constrictions. Posterior to this it gradually 
narrows backward. 


e. Nervous SYSTEM. 


The brain (cb., Figure 19) lies about in the eighth somite. The arrange- 
ment of its ganglionic capsules is peculiar in one respect. The ventral capsules 
of the last brain neuromere (Figure 21) lie side by side, not tandem as in 
the other species described in this paper. In other respects the arrangement 
of capsules is the same as that found in G. stagnalis and G. fusca (Figures 8, 
12, 16, 18). In the individual whose brain is represented in Figure 21, the 
most ventral and posterior capsule of neuromere I. had a horn-like process ex- 
tending back laterally into contact with the lateral capsules of neuromere III. ; 
this condition, however, appears to be unusual. 


46 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


5. Glossiphonia elegans Verrit (1872). 
Plate 7; Plate 2, Fig.5; Plate 3, Fig. 11. 


Clepsine elegans Verrill (72); (2) C. pallida Verrill (’72); C. patelliformis 
Nicholson (’73). 


a. Hapitat, Size, Conor. ; 


This species is very closely related to the European G. complanata L. and G. 
concolor Apathy. Blanchard (’94), indeed, considers it identical with G. com- 
planata L. and regards G. concolor Apdthy as merely a variety of the same 
species. However, both Apathy (88) and Oka (’94) testify to the perfect dis- 
tinctness of G. complanata and G. concolor, which occur together in Europe. 
I have myself compared animals of the species to be described with alcoholic 
specimens of G. complanata from Ziirich, Switzerland, and find certain small 
but constant differences between the two. I shall therefore describe the animals 
which I find here in the vicinity of Cambridge under the name proposed by 
Verrill in 1872, recognizing, however, that they are very closely related to the 
two European species (or varieties) named. 

G. elegans (Plate 7) is found in localities similar to those frequented by G. 
stagnalis, often in company with that species. It is considerably larger, being 
much broader and thicker in proportion to its length, though scarcely longer. 

In its movements it is more sluggish, resembling closely the small G. het- 
eroclita in that regard. It adheres to the side of the aquarium with a tenacity 
displayed by no other of our species except G. parasitica. 

The form of the body at rest is elliptical. | 

The largest individuals which I have collected measure, when alive, as 
follows : — 

Length, fully extended, 28 mm. ; at rest, 14-18 mm. 

Width, fully extended, 5 mm. ; at rest, about 7 mm. 

Color. — Small individuals are usually of a bright, transparent green color. 
Adult animals, viewed with the naked eye or through a hand lens, appear of 
a reddish or greenish brown color, and are darker above than below. 

The head is colorless. The dorsal surface of the body is marked with 
numerous small circular white spots, about the width of a body-ring in 
diameter. These spots are so placed as to form transverse and longitudinal 
rows, just as do the similar spots of G. fusca. The transverse rows fall on the 
sensory (middle) rings of their respective somites, each row containing seven 
spots, when the full number is present. Each of these seven spots falls in a 
different longitudinal row, there being three pairs of rows arranged sym- 
metrically with reference to an unpaired (median) row, exactly as in G. 
fusca. The paired rows may be designated respectively paramedian, inter- 
mediate, and marginal, for they occupy practically the same position on the 
body as do the rows of white spots in the case of G. fusca, and the rows of 
papille in that of G. parasitica (Figure 6). 


CASTLE: NORTH AMERICAN RHYNCHOBDELLIDA). AT 


In addition to the spots which fall into rows as just described, a few spots 
are usually found scattered more or less irregularly over the surface of the 
body. 

Two interrupted brown lines (Figure 30) appear in a paramedian position 
on the dorsal surface, the interruptions being due to the segmentally arranged 
white spots of the paramedian rows. A pair of similar, though fainter, dark 
lines is found on the ventral surface; but they are farther apart, including 
between them about the middle third of the ventral surface. The dorsal para- 
median lines include between them (in the middle of the body) about one 
fourth of the width of the dorsal surface, which part is usually rather more 
heavily pigmented than the more lateral portions. 

A median, clear, unpigmented band extends the entire length of the body 
on the ventral surface. The median row of light spots on the dorsal surface 
often run together in the posterior third of the body, forming a continuous light 
vitta. 

Examining more minutely into the coloration of the animal, one finds that 
it is due to the same two classes of cells as produce the coloration of most other 
species: first, pigment cells proper, — “ excretophores,” Graf; and secondly, 
reserve-food cells. 

The pigment cells proper, as in other species, occupy a superficial position 
in, or immediately underneath, the epidermis. They are stellate or richly 
branched, and are more abundant on the dorsal than on the ventral surface ; in 
small individuals they are almost entirely wanting. The pigment in immature 
animals is a rust-colored or dull reddish-brown, but in full-sized animals it is 
usually dark-brown. 

There is no pigment anterior and lateral to the eyes, nor in the white 
spots already mentioned. The pigment is more abundant than elsewhere 
in the paramedian dark lines, indeed its abundance there produces those 
lines. 

The reserve-food cells in this species, as in G. fusca, are of two forms: first, 
the ordinary form of large reserve-food cell distributed irregularly through the 
deeper parts of the body ; secondly, a special form of reserve-food cell, smaller, 
and more superficial in position, and found only in the white spots already 
described. 

The ordinary reserve-food cells are large and rounded in outline, often at- 
taining a diameter of forty mikra or more. They contain rounded granules of 
a bright green color both by reflected and by transmitted light. It is this 
form of cell which gives to the small, immature individuals their green color, 
and often imparts a greenish tone to the brown-colored adults. 

The special form of reserve-food cell agrees closely both in appearance and in 
distribution with the similarly designated structures of G. fusca. It is found, 
as already stated, only in the white spots of the dorsal surface ; cells of this kind 
occur in a group of from two to a dozen or more each, situated in the centre 
of a white spot, just underneath the epidermis. By reflected light they are of 
a light lemon-yellow color ; by transmitted light, greenish-brown. 

VOL. XXXVI. — No. 2. 3 


48 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


Each of the white spots in the paired rows contains an inconspicuous, low 
rounded papilla (much less prominent than are the papillz of G. complanata, 
so far as my observations go). 

The median row of white spots is less well developed than are the paired 
rows ; in the four or five somites immediately anterior to the anus, it is com- 
monly replaced by a continuous, median, clear vitta, within which is seen a 
narrower band of the lemon-yellow reserve-food cells. 

Obviously the color pattern of this species resembles very closely that of G. fusca, 
although in a majority of characters the animal is more closely related to G. 
parasitica. 


6. Surrace, Rives, Somires, Eyes, Suckers. 


The surface of the body is rather rough, owing to the strong development in 
this species of the integumental sense-organs described by Bayer (98). It 
does not, however, bear conspicuous papille, as is the case with G. parasitica 
and the European G. complanata. The low, rounded papille which are 
found in the paired longitudinal rows of white spots are much smaller than 
the similarly placed papille of G. complanata. In this particular G. elegans 
seems to agree with G. concolor (see Apathy, 88, page 771). 

External rings, as a rule, rounded and distinct, less convex and not pointed as 
are those of G. complanata, sixty-eight in number, distributed as follows : — 

Somites 1—-Iv. uniannulate ; but the boundary between rings 1 and 2 is often 
inconspicuous (compare Figures 28, 29, 30), approaching the condition found 
in G. stagnalis, where somites I. and 11. form a single broad ring, which, how- 
ever, is sometimes divided by a shallow transverse furrow (Figures 3, 7). 

Somites v.-XXIV. triannulate, but the condition of somite v. is peculiar. Its 
anterior annulus (5, Plate 7, Figures 28-31) is commonly narrow and imper- 
fectly separated from the following (sensory) annulus (6). This case illus- 
trates well the initial step in reduction (or final step in elaboration, p. 33) 
of the triannulate somite. It represents an intermediate stage between the 
biannulate and triannulate condition of somite v. seen respectively in G. stag- 
nalis (Figure 7, Plate 3) and G. heteroclita (Figure 20, Plate 5). 

Somite xxv. is biannulate (Figure 28), but the furrow between its two annuli 
is often inconspicuous. Somites XXVI. and XXvH. are commonly uniannulate, 
though notched at the margin of the body, which fact shows that the final step 
in somite reduction (or initial step in somite growth) is not yet accomplished 
in the case of these somites. 

Eyes, six, in two parallel rows close together, in rings 3 and 4 (Figure 30). 
Sometimes the first pair of eyes lies partly in the posterior half of ring 2 
(Figure 29). The middle pair is the largest of the three ; the anterior pair, 
the smallest. The first two pairs are directed obliquely forward, the last pair 
obliquely backward; all are turned away from the median plane (Figures 29, 
30). From the relation of the eyes to the nerves connected with the metameric 
sensille (Figure 29), it is plain that the three pairs of eyes have been derived 
from the sensille of somites I., 111., and Iv. respectively. It is further evi- 


CASTLE: NORTH AMERICAN RHYNCHOBDELLIDA. 49 


dent that the single pair of eyes found in each of the species stagnalis, fusca, 
and elongata corresponds with the middle (largest) pair of eyes of this species, 
the pair belonging to somite III. 
The oral sucker, as in the other species described, lies within somites I.-Iv. 
(Figures 29, 31). 
c. REPRODUCTIVE ORGANS. 


Male genital pore (po. @, Figure 28), between somites XI. and XII. (rings 25 
and 26), a position one ring anterior to that of the same structure in the 
species already described. 

Female genital pore (po. 9, Figure 28), between the second and third rings 
of somite XII. (rings 27 and 28), the usual position of this structure in the 
genus. 

Testes (te., Figure 28), ten pairs. The anterior six pairs occupy the same 
positions as the testes in the species already described, being placed interseg- 
mentally in somites — — . The remaining four pairs occur immediately 
behind those already mentioned ; the most anterior one, between the last 
crop and first stomach diverticulum, in somites = *; the other three between 
successive stomach diverticula, and like them separated by rather less than 
metameric intervals. No other species of Glossiphonia known to me, except 
the European G. complanata, has normally a greater number of testes than six 
pairs. In that species likewise the testes number ten pairs placed exactly as 
in elegans. This is one of several facts showing the very close relationship of 
the two species named. The last one or two pairs of testes are less constant in 
their occurrence than those farther forward. 

Eggs are laid by G. elegans, in the vicinity of Cambridge, in April, May, or 
as late as June. The temperature of the water in the spring undoubtedly 
exercises considerable influence in determining the time of egg-laying.  Indi- 
viduals brought into the laboratory on March 27, 1898, laid eggs nine days 
later. On April 29, 1900, animals of this species bearing eggs were collected 
from Alewife Brook, Cambridge, though G. stagnalis, found with them, appar- 
ently had not yet laid its eggs. The eggs are dull pinkish white in color and are 
borne on the under side of the body in from three to six large clusters, which 
are rather easily detached from the body, if the animal is disturbed. Each 
cluster contains a considerable number of eggs, often as many as twenty or 
twenty-five, enclosed in a delicate sac. The sacs are not arranged sym- 
metrically in two parallel rows, as in G. stagnalis and G. fusca, but quite 
irregularly, a sac being attached either in the median plane of the body or to 
one side of it, as the case may be. 


d. Digestive TRACT. 


The mouth is situated well forward in somite 111., anterior to the eyes, or at 
least anterior to the last two pairs of eyes (Figures 29, 31). 


50 BULLETIN :. MUSEUM OF COMPARATIVE ZOOLOGY. 


The proboscis (p7’b., Figure 28) is long, extending over somites VIII.—xm. 
There is practically no esophagus, as I have used the term, for the pharyngeal 
sac containing the proboscis extends back almost to the beginning of the crop. 

The salivary glands are numerous, often reaching seventy-five or more in 
number in each half of the body. They are scattered usually through somites 
xI.-xvilIl. In Figure 28 they are represented as relatively a little too small. 

The crop (¢glv.) bears seven pairs of large, lateral diverticula directed back- 
ward and often lobed distally. They arise in somites X111.—XIx., always in the 
middle of a somite, as in the other species described. The last pair of crop 
diverticula is, as usual, the largest of all; it may extend back through three or 
four somites, giving off secondary lateral diverticula metamerically, as shown 
in Figure 28. Often, however, when the crop is empty, the last pair of diver- 
ticula is little longer than the preceding pair. 

The stomach (ga., Figure 28) bears, as in other species, four pairs of diverti- 
cula, which arise within the three somites x1x.-xx1. The intestine (in.) extends 
through the six remaining somites, consisting proximally of two distinct cham- 
bers limited by valve-like constrictions and usually situated in somites XXII. 
and xxiu. Distally it is a gradually narrowing tube terminating at the anus 
just behind somite Xxv1. 


e. NePHROPORES, Nervous SYSTEM. 


The nephropores open ventro-laterally, a little anterior to the middle of the 
sensory ring of a somite. The number of nephridia has not been determined 
for this species. 

The brain (cb., Figures 28, 30) lies for the most part in somite vil. The 
arrangement of its ganglionic capsules (Figure 5, Plate 2; Figure 11, Plate 3) 
is usually similar to that found in the brain of G. stagnalis and G. fusca, but 
the capsules are not so closely crowded together, and the supra-cesophageal com- 
missure lies well forward, not being carried back over the middle of the brain 
as in G. stagnalis (Figure 12). The less crowded condition of the capsules in 
this species (Figure 5) explains an abnormality in their arrangement observed 
in the brain of a single individual out of several examined; the two ventral 
capsules of somite 111. (usually found side by side as in G. stagnalis and the 
other species already described) were in this case arranged tandem, just as in 
ganglia in unabbreviated somites. 


Comparing the conditions of the brain capsules in the several species described 
in this paper, one may say that the larger the leech is, the less are its capsules 
crowded. This fact seems to indicate that the capsules, and probably the indi- 
vidual ganglion cells also, do not increase in size proportionally with the growth 
of the leech. This is certainly true of the development of the individual, if not 
also of the race, for in the very young leech the ganglia of the nerve chain oc- 
cur in close succession with scarcely any intervening space, whereas in the adult 
they may be separated by a distance of two rings or even more. 


CASTLE: NORTH AMERICAN RHYNCHOBDELLID®. Bil 


6. Glossiphonia parasitica Say (1824). 
Plate 1, Figs. 2, 3a, 30; Plate 2, Fig. 6; Plate 8, Figs. 32, 33, 37. 


Hirudo parasitica Say (’24) ; Clepsine parasitica Diesing (’50); C. plana 
Whitman (91°); ? C. chelydra Whitman (’91*). 


a. Hasitat, Form, Size. 


This large and conspicuously colored leech is the commonest and most widely 
distributed of our North American species of Glossiphonia. It is often found 
adhering to the bodies of turtles, whose blood it sucks, or underneath stones in 
pools and streams frequented by turtles. It is referable to the genus Placobdella 
Blanchard (°94), if one recognizes the validity of that genus. In it are included 
probably several forms which because of their close relationship I choose to call 
varieties. One of these has been carefully described by Whitman (’91*) under 
the name “‘Clepsine plana.” In what follows I hope to supplement that de- 
scription and add the description of another form which is commonly found 
associated with it. The two varieties agree completely, so far as I can deter- 
mine, in form, size, and constitution of somites, but can be distinguished in my 
collections by constant differences in roughness of surface and in color pattern. 

In general form the body in this species is very broad and flat. Whitman 
describes it correctly in the case of large individuals as “ ovate-elliptical in con- 
traction, emarginate posteriorly.” In the case of small individuals, however, 
or of large individuals well extended, the emarginate condition is not present 
(Figure 6, Plate 2; Figure 37, Plate 8; Figure C, p. 56). The dimensions 
given by Whitman for the largest individuals, I can substantiate: “Length at 
rest, 5-6 cm.; width, 2.6 cm.” I have an alcoholic specimen (var. rugosa) from 
Lake Chautauqua, N.Y., which measures 5.6 cm. in length, and 3 em. in width. 
Another (var. plana) taken from a turtle brought from the Illinois River 
measures 5.5 cm. in length, 2.3 em. in width. A living specimen (var. plana) 
taken from a snapping turtle (Chelydra serpentina) captured near Cambridge, 
Mass., measures at rest 5.8 cm. in length, 2.1 cm. in width. Whitman says 
further : ‘‘ Length in extension, 8.5cm.; width, 1.8 em.” My living Cambridge 
specimen attains in extension a length of about 7.5 cm., in which condition its 
greatest width is 1.5 to 1.7 cm. 


6. Rixes anp Somitss. 


The rings are distinct except at either end of the body. The furrow between 
the anterior and middle rings of each somite is, however, less deep than that 
which separates other rings, for which reason the anterior two thirds of a so- 
mite sometimes appears like a single broad annulus, especially at the margin 
of the body (Figures 2, 3}, Plate1; Figure 6, Plate 2; Figures 32, 33, 37, 
Plate 8). 

Somites 1, 11., and XXV.-XXVII. uniannulate (Figures 6, 33, 37), but xxv. and 


52 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


XXVI. are commonly divided at the margin of the body into a broad anterior 
and a narrow posterior portion. Somites mI. and Iv. are biannulate, the broad 
anterior ring in each case bearing the sensille and representing both the an- 
terior and the middle ring of a triannulate somite (Figure 2, I11.-vI.). The 
remaining preanal somites (v.-xxIv., Figure 6) are triannulate, but the pos- 
terior annulus of xxiv. is narrower than the adjacent annuli (Figure 6), and 
the anterior and middle annuli of somite v. are united ventrally while sepa- 
rated by only a very shallow furrow dorsally (7, 8, Figures 2, 36, Plate 1. 
These two cases illustrate the centripetal progress of abbreviation (or arrested 
development), that part of each terminal triannulate somite being affected 
which is adjacent to an abbreviated somite. 

In Figure 32, Plate 8, is shown a rather unusual condition, the apparent 
disappearance of the furrow separating somites 11. and 111.4 

The total number of preanal rings is sixty-nine, counting somites I., IL, 
and XXV.-XXVII. as uniannulate, 111. and Iv. as biannulate, and V.—xxXIV. as 
triannulate (Figure 6). 


ec. Eyrs, MoutH, Ora Sucker. 


The eyes appear in the living animal, or in whole preparations, as a single 
pair closely united and situated in rings 3 and 4 (somite 111.). See Figure 6, 
Plate 1; and Figures 32, 33, Plate 8. An examination of sections, however, 
particularly of young individuals, shows that there are really three distinct 
pairs of eyes present, there being a small rudimentary pair anterior, and an- 
other still more rudimentary posterior to the principal pair of eyes, exactly as 
shown for “C. hollensis” by Whitman (92, Figure 6). 

All three pairs of eyes? are partially imbedded in a common pigment mass, 
the anterior and middle pairs being directed forward, the posterior pair back- 
ward, just as in G. elegans and G. heteroclita (Figures 20, 29). The largest 


1 A similar condition is figured by Whitman (’91*) in his Plate 15, Figure 1S ie 
his text, however, Whitman says (p. 412): ‘In front of the eyes I was unable to 
discover any distinct rings. In another species C. chelydre, from Wisconsin, there 
are three narrow rings in front of the eyes; and the first is marked by the usual 
metameric sense-organs. Although no metameric sense-organs were recognized 
in front of the eyes in C. plana, the correspondence of other metameric characters 
in the two species is sufficiently close to enable me to identify the ocular rings as 
equivalents. The preocular part of the head is, therefore, probably equivalent to 
the first somite of C. chelydre, and is so numbered in Figure 1.” 

In view of Whitman’s subsequently published studies on “ The metamerism of 
Clepsine ” (92), I think he unquestionably would now recognize two preocular 
somites both in “ C. plana” and in “C. chelydra ”; at any rate, that is the number 
found in the species which I am describing (Figure 2, Plate 1). Since Whitman 
has pointed out no other difference between his “plana” and “chelydre ” than 
the uncertain one of preocular rings, I consider that their specific distinctness 
remains to be established. 

2 Only the largest (middle) pair of eyes appear in the section shown in Figure 2. 


CASTLE: NORTH AMERICAN RHYNCHOBDELLID®. 53 


(middle) pair is closely united with sensille situated in the first ring of so- 
mite 11. (Figure 2), a fact which Whitman (’92) established for ‘¢ C. hollensis” 
and which I can completely confirm for the species under discussion (Figure 2), 

Whitman (’92) further established the fact that the anterior pair of eyes 
in “hollensis”’ originates in connection with the sensille of somite um. He 
gives no statement as to the origin of the posterior pair. Comparison with G. 
elegans (Figure 29), however, leads me to regard this pair as probably derived 
from the sensillee of somite Iv. If so, the condition of the eyes in parasitica 
can be derived in its entirety from that found in G. elegans by supposing that 
both the anterior and the posterior pairs of eyes have become rudimentary and 
been brought close to the large middle pair. 

The mouth (or., Figure 2) apparently lies between somites I. and 11. ; in other 
species it lies farther back, usually in the anterior part of somite 111. The oral 
sucker is formed by somites I.-IV., as in other species. 


d. REPRODUCTIVE ORGANS. 


The genita? pores are situated in this species exactly as in G. elegans; the 
male (po. @, Figure 36), between somites xI. and XII. (rings 27 and 28) ; 
the female (po. 9), between the middle and posterior annuli of somite x11. 
(tings 29 and 30). 

XA.) SXVEL. 


Testes, six pairs situated intersegmentally in somites ——— _ 


, the usual 
Vee eRKe 


position in the genus. 

The eggs are large, white, and opaque. In the vicinity of Cambridge they 
are laid in May and June, perhaps also in July. In the case of those animals 
which laid in the laboratory, the eggs appeared to be attached loosely in a sin- 
gle group of fifty or more to the side of the aquarium, rather than to the body 
of the leech as is the case in the other species studied. The leech remained 
closely arched over the eggs, —a position from which it was removed only 
with great difficulty. 


e. Digestive Tract. 


The digestive tract resembles very closely that of G. elegans, but has one 
strikingly distinctive feature : the salivary glands (gl. sal., Figure 36), instead 
of being distributed through several somites in the crop region, are closely 
aggregated into two compact groups in each half of the body, these groups lying 
symmetrically, a pair on either side of the proboscis, within somites 1x.—xI. 


1 On account of this and other close structural agreements with “ C. hollensis ” 
as described by Whitman (’92), I was for some time inclined to regard that name 
as well as “ chelydra ” as a synonym with parasitica, and I have so treated it in a 
recent publication (Castle, 1900). Professor Whitman, however, has subsequently 
informed me ina letter that in hollensis “there are several pairs of pigmented eyes 
behind the pair usually recognized as ‘eyes.’ These are quite conspicuous in the 
living leech, and I have never seen any such feature in other Clepsines.” This 
being so, it is probable that hollensis should rank as a distinct species. 


54 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


The crop bears seven pairs of lateral diverticula, as in G. elegans and the 
closely related European G. complanata, with both of which this species has 
many points in common. The first pair of diverticula arise in the anterior or 
middle part of somite x11. and are two or three lobed, the anterior lobe being 
prolonged forward through somites x11. and x1. The five following pairs of 
crop diverticula arise in the middle of somites xtv.—xvim. respectively, and 
are usually bilobed distally. The last (seventh) pair of crop diverticula ex- 
tend far back of their origin in somite xrx., often into somite xxm. They 
give off secondary lateral diverticula, a pair in each of the somites through 
which they extend. 

The crop diverticula are often a conspicuous feature of this species when 
viewed in a living condition from the ventral side of the animal, for numerous 
large green chromatophores aggregate about the crop and show through the 
clear ventral body wall the form of the crop outlined in green. 


f. Nepuropores, NERVOUS System. 


The nephropores (nph’po., Figure 36) open ventrally, anterior to the middle 
of the sensory ring of a somite, as stated by Whitman (91°). They are present 
in the eighth and all the following triannulate somites. 

I have nothing new to add to Whitman’s (’92) excellent account of the cen- 
tral nervous system. It is important to notice, however, the arrangement of the 
ventral capsules in the brain region (Figure 36). Those of neuromeres 111.—VI. 
all lie in a single row in the median plane; that is, have what I have called the 
tandem arrangement. The ventral capsules of neuromere I. (2, 2, Figure 3 b) 
have the side-by-side position found in all the species examined by me. 

Figure 3 a is a dorsal view of the brain and shows that the supra-cesophageal 
commissure in the species lies far forward in what may well be regarded as 
its primitive position. 

The less crowded condition of the brain capsules in this as compared with 
other species is interesting, as showing that the smaller the leech is, the more 
crowded are its brain capsules likely to be (compare page 50). 


g. PAPILLE, COLORATION. 


I have reserved to the last, in describing this species, the discussion of papil- 
le and coloration, for it is on the basis of these characters alone that I am able 
to distinguish two varieties, plana and rugosa, which I find associated together, 
but apparently without intergrading forms, in collections from Cambridge, 
Mass., Lake Chautauqua, N. Y., Lake Forest, I]., and Wellsville, Kan., a very 
wide range extending across the Mississippi valley and the Atlantic seaboard. 


(1) Var. plana Clepsine plana Whitman, ’91*). 


This variety has a relatively smooth skin, which bears dorsally small dome- 
shaped papill@, the most conspicuous of which are placed as indicated by stars 


CASTLE: NORTH AMERICAN RHYNCHOBDELLIDA. 55 


in Figure 6, Plate 2. They include five longitudinal rows of papille found on 
the middle (sensory) annuli of usually all the triannulate somites. These rows 
may be designated, from their position, median, marginal, and intermediate, the 
first named being unpaired, the other two paired. 

A row of papille is found also between the median and each intermediate 
row, but these papille are situated not on the middle, but on the posterior 
annulus of each of the somites from about yu. to xxi. inclusive (Figure 6). 
These will be designated paramedian rows. 

The most conspicuous papille of somites xxv.-xxvir. are usually placed as 
indicated in Figure 6. They consist, first, of a continuation of the marginal 
rows back to the anus; secondly, of two rows of three papillae each, placed one 
on either side of the median plane and too near it to fall in the paramedian 
rows found farther forward. 

Other less conspicuous papille occur on the dorsal surface of the body and 
posterior sucker, but no papille are found on the ventral surface of the 
animal. 

The general color of the body above is brown variegated with yellow, orange, 
and green. Light areas of yellow or pale orange form : — 

I. A median vitta extending from the anterior end of the body back to somite 
xxv., usually without interruption, but not always so, and expanding commonly 
at six places, namely, (1) in somites vi. and vi. (Figure 32, Plate 8) ; (2) in 
somite 1X.; (3) in somites xu. and xmt.; (4) in somites xy. and xvr.; and 
(6) in somite xxi. (and the posterior part of somite xx1.). The median row 
of papillae already described falls entirely in the median light vitta. In somites 
XXV.-xxvil. both vitta and papillz become double, dark pigment being found 
along the median line back to the anus, usually behind it also quite to the 
posterior margin of the acetabulum. The double (or paramedian) light vitta 
of somites XXV.-XXVII. contains the three pairs of papille shown in Figure 6, 
Plate 2 ; it may or may not be continuous with the median light vitta farther 
forward. 

II. Throughout the greater part of the body the papille of the intermediate 
rows lie each in an irregularly rounded light spot. The successive spots of 
each half of the body may become confluent so as to form an irregular, 
frequently interrupted, longitudinal band. 

III. The margins of the body are conspicuously marked with metameric 
light spots from about the third or fourth somite back to somite xxv. Some 
idea of the form and position of these spots may be obtained from an examina- 
tion of the stippled areas in Figure 6, Plate 2, and Figure 32, Plate 8. Each 
spot is typically V- or U-shaped and is placed on the adjacent non-sensory rings 
of two successive somites. The usually hollow centre of the V or U is formed 
by a spot of brown sometimes bordered with orange. The margin of the sen- 
sory ring is generally darker in color than its more median parts, so that it is 
strongly in contrast with the metameric light spots which it separates. 

The posterior sucker is decorated with radially placed triangular light spots 
(Figure 6) resembling the marginal spots of the body. Other irregularly 


56 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY.. 


rounded light spots may be found on the dorsal surface of the body in light- 
colored individuals, usually associated with certain papille. 

There is a certain correlation in the development of light spots in different 
parts of the body ; an animal which has a well-developed median vitta will 
also have conspicuous marginal and intermediate light spots and vice versa. 

The ventral side of the body is much lighter in color, marked only by a 
few longitudinal bands of dull brown or greenish brown. The number of these 
bands is either eleven or twelve according as there is present, in addition to 
five pairs of bands laterally placed, a single broad median band or a pair of 
narrow paramedian bands separated by an irregular median clear band. 

From the under side of the body one can often see in living animals the green 
pigmented crop diverticula showing through the semi-transparent body. 


Figure C.— G. parasitica, var. rugosa. Dorsal view of posterior part of body, 
showing position and approximate relative size of papilla. From a Cam- 
bridge, Mass., individual. 


(2) Var. rugosa, var. nov. 


The dorsal surface of the body is much rougher in this variety, the papille 
being larger, more numerous, and structurally more complex. Instead of being 
simple, low, and dome-shaped, the more conspicuous papille are extended dis- 
tally in several divergent whitish points, giving the body a decidedly rough, 
harsh feeling to the touch in the case of hardened specimens. The larger 
papille are likewise rendered more conspicuous by the fact that they are 
commonly unpigmented, though placed in a generally dark background. 

The arrangement of the principal rows of papille on the dorsal surface is 
similar to that in G. plana, but with the following easily determined and con- 
stant difference. In somites xxi. and xxiv. (Figure C), the median row of 
papille becomes inconspicuous or disappears altogether, and a large papilla 
appears on either side of the median line, on the sensory ring of each somite. 
The ventral surface is free from papille as in plana. 


CASTLE: NORTH AMERICAN RHYNCHOBDELLID®. Bi 


The color pattern is somewhat similar to that of plana, but the contrasts are 
less striking and the colors less brilliant. The general color effect of the dorsal 
surface is a grayish brown. Marginal spots of light yellow are present, as in 
plana, on the non-sensory rings, but they are smaller and do not extend so far 
mesiad from the margin of the body. Practically all the larger papille appear 
as small white spots in a generally dark background. 

The median vitta is not a continuous light band as in plana, but is inter- 
rupted at regular intervals by spots of a darker color than the general dorsal 
surface. It begins as a narrow median light band on the head and neck, con- 
stricted or sometimes interrupted in the posterior part of somite v1., less often 
constricted or interrupted in somite v. also. About in annulus 19, somite rx., 
begins a narrow dark band which continues to the middle of somite xtr. 
Then come alternating light and dark spots, three of each. A light spot ex- 
tends over four annuli, a black spot over five as follows: Light spots, annuli 
29-32 (Figure 6), 38-41, 47-50; dark spots, annuli 33-37, 42-46, 51-55. An- 
other light spot covers rings 56-64 or 65, broadening out posteriorly so as to 
include the paired papille of somites xxii. and xxiv. (Figure C). This is fol- 
lowed by a median dark spot extending back past the anus to the margin of 
the posterior sucker. 

The posterior sucker is marked by alternating light and dark rays, very 
much as in plana (Figure 6); it also bears papille like those of the body 
farther forward. 

Ventrally the body is light gray in color, owing to the presence there of 
scattered pigment flecks, which, however, are not arranged in longitudinal 
bands as in plana. 


V. MUTUAL RELATIONSHIPS OF THE SPECIES 
DESCRIBED. 


The species described in this paper, with the exception of heteroclita, 
fall naturally into two distinct groups (Figure D, page 58), which may 
be designated respectively the stagnalis and the parasitica groups. The 
former includes the three species stagnalis, elongata, and fusca; the 
latter, parasitica and elegans, with the closely related European species, 
complanata and concolor. Heteroclita occupies a somewhat isolated 
position intermediate between these two groups. 

As arranged in Figure D., the species form a series in which there is 
from left to right an increasing degree of complexity of structure. This 
appears from an examination of rugosity, somite structure, crop diverti- 
cula, and certain other characters. 

In the species of the stagnalis group (1) there is a single pair of eyes 
derived from the sensillee of somite 111., (2) the genital pores are separated 
by a single ring, namely, the middle (sensory) ring of somite x11, and 


58 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 


(3) the crop diverticula are simple and never exceed six pairs in number, 
(4) All three species are small, (5) have relatively smooth skin, and (6) 
at least two of them bear the eggs in clusters attached symmetrically in 
a double row to the under side of the body, the condition in the third 
species being unknown. 

In parasitica and elegans (1) there are three pairs of eyes derived 
respectively from the sensilla of somites 11, 11, and tv., (2) the genital 
pores are separated by two rings, the anterior two rings of somite XII, 
(3) the crop diverticula number seven pairs and are lobed, (4) the in- 
tegument is rough and bears papille, (5) the attachment of the egg 


heteroclita 
fusca elegans 
stagnalis \ concolor 
‘ yi 
elongata \ / complanata 


\ 


| Lea 


\ \ parasitica 
\ \ ie 
\ 


Nell 7 


Ficure D. Diagram indicating relationships of the species described. 


clusters to the body, when such attachment exists, is imperfect and the 
arrangement of the clusters irregular. 

The European species complanata and concolor are very closely 
related to elegans, complanata certainly, perhaps also concolor, being 
intermediate between it and parasitica. 

In view of the many points of similarity between parasitica and com- 
planata, there seems to me to be insufficient ground for placing them in 
distinct genera, as proposed by Blanchard. 

Allusion has already been made to the somewhat isolated position of 
heteroclita. In size and in the character of its integument, it resembles 
the stagnalis group, likewise in the number of its crop diverticula ; in 
regard to the lobed condition of its crop diverticula, it resembles the 
parasitica group. In the number of its eyes (three pairs), it likewise 
resembles the latter group, but the derivation of these apparently is from 
different somites (111.-v. in heteroclita, 11.-Iv. in parasitica and elegans.) 
As regards the position of the genital pores and the way the eggs are 
borne, it differs alike from both groups. 


CASTLE: NORTH AMERICAN RHYNCHOBDELLID. 59 


VI. PARASITES. 


Three different endo-parasites, of which I find no notice in the litera- 
ture, in addition possibly to one already described by Bolsius (96), 
infest more or less commonly the species of Glossiphonia found in the 
vicinity of Cambridge, Mass. One of these is a small nematode, another 
a trematode, these two having been observed in the body of G. stagnalis 
only ; the third is a sporozodn found in at least four of the species 
described in this paper. 

In January, 1898, I first observed a minute nematode parasite wrig- 
gling about in the central lacunar space of a live G. stagnalis. Another 
similarly parasitized leech was found upon further search, and a third 
was found in the following March, the ovary of the host containing at 
that time full-grown eggs. ‘The parasite in the last-mentioned case lay 
close to the contractile dorsal blood-vessel, a very common position for 
it, as subsequent observations showed. In the spring of 1899 several 
parasitized individuals were collected and studied; and others were 
observed in the fall of 1899. 

The length of the parasite is about the same in the case of all 
individuals examined ; namely, 1.43 mm. In form, the worm is slender 
and thread-like, being widest near the middle of its body, where it 
measures 0.027 mm. in breadth. From there it tapers almost imper- 
ceptibly toward either end. The posterior end of the body is sharply 
pointed ; the anterior end blunt, its centre being occupied by the very 
minute, conical mouth. 

Examination of a large number of individuals of G. stagnalis in the 
spring of 1899 showed that between five and ten per cent of the indi- 
viduals taken from a particular pond, in which the species abounds, 
contained the nematode parasite. Usually only a single parasite has 
been observed in the body of a host, but in one case there were three. 

The nematode is generally found either coiled up (but not encysted) or 
wriggling about in the central lacuna (body cavity), in the middle or 
toward the posterior end of the body. The presence of the parasite 
does not seem seriously to inconvenience its host, for the parasitized 
individuals are as large and well developed as those free from parasites, 
and contain sexual products in equal abundance. 

Parasitized individuals were-kept in aquaria for several weeks without 
the occurrence of any noticeable change in the condition of the parasites. 
This fact and the manifest immaturity of all the parasites examined 
makes me believe that the leech is an intermediate host and that the 


60 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


nematode probably attains maturity after passing from the body of the 
leech into that of another host, perhaps some fish, which feeds upon 
the leech. How the nematode gets into the body of the leech is likewise 
unknown, probably from the body of some snail or other small pond 
animal on which the leech feeds. 


The supposed trematode parasite I have observed but once, in Novem- 
ber, 1899, when three individuals were observed encysted in a single G. 
stagnalis. Unfortunately they with their host died in captivity before 
I had an opportunity to study them carefully. They lay imbedded in 
the deeper muscle layers of their host’s body, toward its anterior end, 
each enclosed in a delicate rounded cyst. A single ventral sucker was 
observed in the parasite and this seemed to lie a little nearer one end 
of the body. Toward the opposite end, a dark granular substance was 
observed in the interior of the body, probably in the digestive tube. 
My study of the parasite, was so incomplete that I should not feel war- 
ranted in asserting the absence of a second sucker more nearly terminal 
in position than the one observed. No measurements of the cysts were 
made, but I should estimate their diameter roughly at 0.50-0.75 mm, 


About half of the individuals of G. elongata which have come under 
my observation contain a gregarine which appears to be identical with 
that described by Bolsius (’96) as occurring in G. complanata (Clepsine 
sexoculata). I have not, however, made a sufficiently careful study of 
it to enable me to add anything to his account. I find the parasite 
attached always to the wall of the stomach diverticula (Figure 27, ga.), 
never in crop or intestine. 

A majority of the individuals of G. fusca collected by me contain 
sporozoa in an encysted condition. These parasites are quite common 
also in the body of G. heteroclita and that of G. elegans, and I have 
found them in a single individual of G. stagnalis. 

Whether or not they represent another stage of the gregarine found 
in G. elongata, I am unable to say. As already indicated, I have ob- 
served them only in stages of encystment, more or less advanced. One 
finds the heavily staining sporocyst in whole preparations of its host, 
usually near the margin of the body, imbedded in the deeper-lying 
muscle layers (longitudinal and dorso-ventral). The sporocysts which 
I have observed were spherical in form; the largest ones examined were 
about 0.13 mm. in diameter and were protected by a thick, dense wall. 
I have not yet been able to obtain sporocysts containing fully formed 


CASTLE: NORTH AMERICAN RHYNCHOBDELLIDA. 61 


spores. Data, accordingly, are wanting for a full description of this 
parasite, as well as of the others mentioned, and only a portion of its 
life history is known. Nevertheless I insert this notice in the hope 
that some one else may be able hereafter to make use of my fragmentary 
observations. 


CampBripeGs, Mass., June, 1900. 


62 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


Bis EEO G heAP a Y- 


Apathy, S. 
°88. Sitsswasser-Hirudineen. in systematischer Essay. Zool. Jahrb., 
Abth. f. Syst., Bd. 3, pp. 725-794. 
Apathy, S. . 
°88*. Analyse der ausseren Korperform der Hirudineen. Mitth. Zool. Sta. 
Neapel, Bd. 8, pp. 153-232, Taf. 8, 9. 
Bayer, E. 
°98. Hypodermis und neue Hautsinnesorgane der Rhynchobdelliden. Zeit. 
f. wiss. Zool., Bd. 64, pp. 648-696, Taf. 23-25, 10 Textfig. 
Blanchard, R. 
°94. Hirudinées de I’Italie continentale et insulaire. Boll. Mus. Zool. ed. 
Anat. comp. Torino, Vol. 9, n. 192, 81 pp., 30 Fig. 
Bolsius, H. 
96. Un parasite de la “Glossiphonia sexoculata.” Mem. Pontif. Accad. 
Nuovi Lincei, Vol. XI., 5 pp., 1 Pl. 
Bristol, C. L. 
°99. The Metamerism of Nephelis. Jour. of Morph., Vol. 15, pp. 17-72, 
Pls. 4-8. 
Budge, J. 
49. Clepsine bioculata Savigny. Verh. d. naturh. Vereins preuss. Rhein- 
lande, Bd. 6, pp. 89-155, Taf. 5, 6. 
Castle, W. E. 
1900. The Metamerism of the Hirudinea. Proc. Amer. Acad. Arts and 
Sci., Vol. 35, pp. 285-303, 8 Fig. 
Diesing, K. M. 
°50. Systema helminthum. 8vo, 2 vol., Vindobonae. 
Graf, A. 
°99. Hirudineenstudien. Abhandl. Leop.-Carol. Akad. d. Naturf., Bd. 72, 
Nr. 2, pp. 217-404, Taf. 1-15, 26 Textfig. 
Gratiolet, P. 
’'62. Recherches sur l’organisation du systeme vasculaire dans la sangsuc 
médicinale et l’aulostome vorace. Ann. Sci. Nat., Zool., T. 17, pp. 175-225, 
Pliie 
Johnson, J. R. 
16. Observations on the Hirudo vulgaris. Phil. Trans. Roy. Soc. London, 
pp: 18-21, Pl. 4. 
Lee, A. B. 
°96. The Microtomist’s Vade-mecum. Fourth edition. Philadelphia. 


CASTLE: NORTH AMERICAN RHYNCHOBDELLIDA. 63 


Linnaeus, C. 
1758. Systema Naturae. 10th edition. 
Moore, J. P. 
°98. The Leeches of the U. S. National Museum. Proc. U. 8. Nat. Mus. 
Vol. 21, pp. 543-563, Pl. 40. 
Moore, J. P. 
1900. A Description of Microbdella biannulata, with Especial Reference to 
the Constitution of the Leech Somite. Proc. Acad. Nat. Sci. Philadel- 
phia, pp- 50-75, Pl. 6. 
Moquin-Tandon, A. 
46. Monographie de la famille des Hirudinées. 8vo, 448 pp. Atlas, 
14 Pl. Paris. 
Miiller, O. F. 
1774. Vermium terrestrium et fluviatilium, ete. 4to. Vol. 1, Havniae et 
Lipsiae. (See Vol. I., “ Helminthica,” p. 49.) 
Nicholson, H. A. 
"73. Contributions to a Fauna Canadensis; being an Account of Animals 
dredged in Lake Ontario in 1872. Canadian Journal, Vol. 18, pp. 490- 
506, 4 Textfigs. 
Oka, A. 
94. Beitrige zur Anatomie der Clepsine. Zeit. f. wiss. Zool., Bd. 58, pp. 
79-151, Taf. 4-6. 
Savigny, J. C. 
20. Systéme des Annélides. Folio, Paris. 
Seay ate 
24. Zoology. Keating’s Narrative of an Expedition to the Source of St. 
Peter’s River, ete., in 1823, under S. H. Long. 2 vols. Philadelphia. 
Vol. 2, pp. 2538-378, Pl. 14, 15. 
Verrill, A. E. 
74, Synopsis of the North American Fresh-Water Leeches. Rept. U.S. 
Fish Commissioner for 1872-3, Pt. 2, pp. 666-689. 
Whitman, C. O. 
85. The External Morphology of the Leech. Proc. Amer. Acad. Arts and 
Sci., Vol. 20, pp. 76-87, 1 PI. 
Whitman, C. O. 
°91. Spermatophores as a Means of Hypodermic Impreguation. Jour. of 
Morph., Vol. 4, pp. 361-406, PI. 14. 
Whitman, C. O. 
914 Descriptior { Clepsine plana. Jour. of Morph., Vol. 4, pp. 407-418, 
PE US: 
Whitman, C. O. 
92. The Metamerism of Clepsine.. Festschr. Leuckarts, pp. 385-395, PI. 
39, 40, Leipzig. ' 


a 


64 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


EXPLANATION OF PLATES. 


All figures were drawn with the aid of Abbé’s camera lucida, unless otherwise 


stated in the explanation of figures. 


Arabic numerals in the figures designate rings, which, except in the case of Fig- 
ures 23 and 27, Plate 6, are numbered from the extreme anterior end of the body 
backward; Roman numerals designate somites numbered in the same manner. 


ABBREVIATIONS. 
act. Acetabulum (posterior sucker). oc. 
an. Anus. @. 
cb. Brain. or. 
dt. ej. Ejaculatory duct. po. & 
ga. Stomach. po. 2 
gl. d. Dorsal gland. pr. 
gl. sal. Salivary glands. sac. phy. 
in. Intestine. suc. or. 
Vglv. Crop. te. 
lac. marg. Marginal lacuna. va. df. 
nph’po. Nephropore. va. ef. 


oa. Ovary. vs. Sem. 


Eye. 

(Esophagus. 
Mouth. 

Male genital pore. 
Female genital pore. 
Proboscis. 
Pharyngeal sac. 
Oral sucker. 
Testis. 

Vas deferens. 
Vas efferens. 
Seminal vesicle. 


Fig. 


Fig. 


Fig. 


Fig 


CasTLe. — Rhynchobdellide. 


3a. 
. 3). G. parasitica. Ventral view of anterior part of a small individual obtained 


PACs 


G. stagnalis. Entire digestive tract shown; somite limits indicated by 
transverse lines, rings not represented. From an entire preparation. 
x about 16. 

G. parasitica. Parasagittal section of head end of a small individual taken 
from a turtle (probably Chelopus insculptus Le Conte) bought in a 
Philadelphia market. Only one (the largest) of the three closely asso- 
ciated pairs of eyes appear in the section. 

G. stagnalis. Ventral view of head end, showing mouth, oral sucker, and 
the marginal sensille and annulation of somites 1.-v1. From an entire 
preparation. X 83. 

G. parasitica. Dorsal view of brain. 


from the same source as that shown in Figure 2. From an entire 
preparation. 


- CASTLE-RHYNCHOBDELLIDAR. : _® Puate 1. 


[od POEs ese) ith Bos 


CasTLE, — Rhynchobdellide, 


PLATE 2. 


Fig. 4. G@. stagnalis. Diagram showing annulation, central nervous system, repro- 
ductive organs (male in left, female in right half of figure), nephropores, 
etc. The outline of the body was drawn from a whole preparation (X 
about 16); everything else is diagrammatic, representing the average 
form and position of organs as determined by examination and com- 
parison of several individuals. 

Fig. 5. Brain of G. elegans, ventral view. From an entire preparation. X 52. 

Fig. 6. G. parasitica. Dorsal view of a young individual from Havana, Illinois, 
partially extended. X about 10. The starlike structures indicate 
papille ; not all of those shown were observed in the individual figured, 
some being supplied from the study of larger individuals in which the 
papille are more conspicuous. 


ASTLE-RHYNCHOBDELLIDAR. PLATE 2. 


B Meisel, {iti Boston 


CasTLe. — Rhynchobdellide. 


esas 
Fig. 8. 
Fig. 9. 
Fig. 10. 
Fig. 11. 
Fig. 12. 


PLATE 3. 


G. stagnalis. VParasagittal section of anterior part of body. X 96. 

G. stagnalis. Brain viewed from left side. Reconstructed from sections. 
> 208. Roman numerals designate segmental nerves; Arabic numerals, 
the ganglionic capsules which supply nerve fibres to same. 

G. stagnalis. Posterior part of ventral ganglionic chain, dorsal view, 
reconstructed from frontal sections. Arabic numerals designate ven- 
tral ganglionic capsules; Roman numerals, metameric nerve bundles. 
x 170. 

G. stagnalis. Diagram showing the arrangement of ganglionic capsules 
on the ventral surface of brain. 

G. elegans. Dorsal view of brain. 

G. stagnalis. Dorsal view of anterior part of brain. From frontal sec- 
tions combined. X 167. 


B Meisel, lith. Boston 


PLATE 3. 


an 


as 0 
c ; \ x i 7 


~CASTLE-RHYNCHOBDELLIDAE... 


WEG. del. 


Fig. 


Fig. 
Fig. 


Fig. 
Fig. 


Fig. 


CasTLe. — Rhynchobdellidie. 


13. 


PLATE 4. 
G. fusca. 


Dorsal view of a small individual. For clearness furrows between 
annuli are represented only at the margin of the body, except where 
they mark somite boundaries. Testes are shown only in the right half 
of the figure, salivary glands only in the left half. From an entire 
preparation. XX about 34. 

Parasagittal section of head end.  X 52. 

Head end of young individual viewed from left side. From an entire 
preparation. XX 83. 

Head end of individual shown in Figure 18. Dorsal view. X 83. 

Group of reserve-food cells from one of the segmental clear spots marking 
the sensory annuli. From a living animal. 865. 

Ventral view of brain. From an entire preparation. X 208. 


CASTLE-RHYNCHOBDELLIDAE. Pate 4 


B.Meisei, lith. Boston 


= band 
> <a 
[a 


oD — 
—_ @ sit 


= 


: 
j 
im 
i 
< 
iat 
| 
Ay iN 
- 
“7 
: 
7 
. 


CasTLE. — Rhynchobdellide. 


Fig. 19. 


Fig. 20. 


Fig. 21. 
Fig. 22. 


PLATE 5. 
G. heteroclita. 


Dorsal view of a rather small individual. For clearness furrows between 
_annuli are shown only at the margin of the body, except where they 

mark somite boundaries. Salivary glands are shown only in the right 
half of the figure, testes only in the left half. From an entire prepara- 
ration. X 62. 

Combination of two or three successive parasagittal sections of head end, 
X 83. 

Brain viewed from the left side. From several sections combined. 

Ventral view of a living animal bearing eggs. X about 13. 


GASTLE-RHYNCHOBDELLIDAE. , Prare 5S. 


AVE 


XVI. 


AVL 


WE.C. del B. Meisel, lith. Boston 


CasTLE. — Rhynchobdellidz. 


PLATE 6. 


G. elongata. 


All figures of this plate were drawn from whole preparations. Annuli in Figures 
23 and 27 are numbered from the posterior margin of the oral sucker backward. 


Fig. 23. 
Fig. 24. 
Fig, 25. 
Fig. 26. 
Fig. 27. 


Head end viewed from right side. 

Posterior end of body viewed from right side. 

Brain, ventral view. 

Brain viewed from right side. 

Ventral view of entire animal partially contracted. In somites v11.—xxII. 
furrows betweem annuli are shown only at the margin of the body, 
except where they mark somite boundaries. 


2 -RHYNCHOBDELLIDAE. | PLATE 6. 


Sous 


Bene ee 
ee V1 
25 


AVE 


4 ys. SEM. 
40 


es st gl 


FZ 


FO 


: B. Meisel, lith. Boston 


CasTLE. — Rhynchobdellide. 


Fig. 28. 


Fig. 29. 
Fig. 30. 
Fig. 31. 


PLATE 7. 
G. elegans. 


Dorsal view of a young individual. In somites v1.-xxv. furrows between 
annuli are shown only at the margin of the body, except where they 
mark somite boundaries. Reproductive organs and salivary glands 
drawn from other, older individuals; salivary gland cells a little too 
small. From an entire preparation. 

Parasagittal section of head end. 

Head end, dorsal view. From an entire preparation. > about 50. 

The same, ventral view. 


WE.C. del. B Meisel, lith. Boston. 


Fig. 


Fig. 
Fig. 
Fig. 
Fig. 


Fig. 


Fig. 


CasTLe. — Rhynchobdellide. 


33. 


36. 


37. 


38. 


PLATE 8&8. 


G. parasitica, var. plana. Dorsal view of head end of an individual from 
Hayana, Illinois, in which the division between rings 2 and 3 was not 
evident. Stippling shows position of yellow pigment in a median vitta 
and (on left side) in metameric marginal spots. From an alcoholic 
specimen. X 41. 

G. parasitica, var. rugosa. Dorsal view of head end of an individual from 
Cambridge, Mass., showing the usual annulation of somites 1.-111. From 
an alcoholic specimen. Enlarged. 

G. stagnalis. Dorsal view of posterior end of body. Enlarged. 

G. heteroclita. Dorsal view of head end of a living animal, showing most 
common position of eyes. Enlarged. 

A dorsal view of the head end of the individual represented in Figure 
88. The anterior ring of somite vI. is seen to contain traces of a trans- 
verse pigment line. Drawn from the living animal. Enlarged. 

G. parasitica, var. plana. Dorsal view of posterior end of body of the 
individual shown in Figure 32. Marginal light spots indicated by 
stippling. 24. 

G. heteroclita. Dorsal view of a living animal, showing the general form 
of the body at rest, and the color pattern sometimes present on the 
dorsal- surface. The rings are not indicated, but the numerals are 
placed opposite and serve to designate those rings in which the 
pigment is found (the anterior rings of their respective somites). 
Enlarged. 


Sika eee 


CASTLE-RHYNCHOBDELLIDAR. 
: “w=, 


PLATE 8. 


os meee = 


NXVI. 


XXVIL. 69 


San. 


; 


7 
B. Meisel, lith. Bastin 


_ _ : 
— 7 xe 
7 = - 
an = ' i 
‘ a= 
¢ 
« 


OM THE GREEN RIVER 
pW OMING, 2025. = 


R. Easrmay, 
es = Wirn Two PLares. 
- CAMBRIDGE, MASS, U.S. A. : | 
PRINTED oR THe MUSEUM 
Sa se “Aveusr, 1900. 
2 es a : | 


Bulletin of the Museum of Comparative Zoology 
AT HARVARD COLLEGE. 
VoL. XXXVI. No. 3. 


FOSSIL LEPIDOSTEIDS FROM THE GREEN RIVER 
SHALES OF WYOMING. 


By C. R. Eastman. 


WitH Two PLArEs. 


CAMBRIDGE, MASS., U.S. A. : 
PRINTED FOR THE MUSEUM. 


Aveust, 1900. 


‘4, 


No. 3. — Fossil Lepidosteids from the Green River Shales of 
Wyoming. By C. R. EASTMAN. 


FY 


Tue Eocene Green River Shales of Wyoming have long been noted for 
their numerous and beautifully preserved fossil fishes, and large collections 
have found their way to various American and foreign museums. Dur- 
ing the summer of 1899 the Museum of Comparative Zodlogy purchased 
of Mr. D. C. Haddenham, a local collector at Fossil, Wyoming, two 
remarkable specimens from the fishbearing shales near that well-known 
locality. One of these is a gigantic Lepidosteid, of which only detached 
fragments have hitherto been known, the other is a nearly perfect 
skeleton of a gallinaceous bird. Both specimens are unique in their 
way, and possess considerable scientific as well as intrinsic value. The 
news of their discovery was first communicated by Professor Wilbur C. 
Knight, of Laramie, Wyoming, who made a special visit to Fossil for 
the purpose of examining the remains, and whose favorable report 
induced their acquisition. 

A brief account of the two specimens, accompanied by a photo-repro- 
duction of the bird, was prepared soon after their arrival in Cambridge, 
and published in the Geological Magazine for February, 1900. Later it 
developed through correspondence with Mr, F. A. Lucas, Curator of 
Comparative Anatomy in the United States National Museum, that this 
Museum had also obtained during the past summer a large cranium of 
Lepidosteus from the same horizon and locality. Another nearly com- 
plete fossil gar which had been exhibited at the World’s Fair in 1893 
was reported, and Mr. Lucas was fortunate enough to ascertain its 
whereabouts and finally to obtain it too for the national collection. 
Descriptions of these three specimens are given in the presént paper, 
and it is to be observed that these are the only noteworthy remains of 
Lepidosteus that have yet been found in the American Eocene. 

The discovery of fossil gars in the Tertiary of this country was first 
reported by O. C. Marsh (Proc. Acad. Nat. Sci. Phil., 1871, p. 105). 
He named two species, Lepidosteus glaber and L. whitney?, both from the 
Eocene of Wyoming ; but as no descriptions were given beyond the bare 
statement that the first “has unusually short vertebra” and the other 

VOL, Xxxvi.— No. 3. 


68 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


has them ‘‘ proportionally longer,” these names were deservedly rejected 
by Cope as nomina nuda. 

A number of species have since been described by Leidy and Cope, all 
founded on more or less fragmentary remains such as detached vertebra, 
scales, and cranial fragments. The only one represented by a tolerably 
complete individual is Z. cuneatus (Cope) from the Miocene of Central 
Utah, the type of which is about 30 cm. in length. The remainder are 
characterized by A. S. Woodward in his Catalogue of Fossil Fishes as 
“all too imperfect for specific, and the majority even for generic deter- 
mination.” For instance, Leidy’s ZL. notabilis is founded on a single 
vertebral centrum, which may or may not be identical with those 
described by him as L. atrox. The type species of “ Clastes,” L. cycli- 
jerus (Cope), is founded on a few cranial bones and scales. There is 
still less reason for regarding “ Pneumatosteus” as a distinct genus, the 
type of P. nahunticus Cope being an opisthoceelous vertebral centrum 
from the Miocene of North Carolina. 

It is obvious from the foregoing that all the specific titles applied to 
fossil gars from this country, with the single exception of LZ. cuneatus, 
have had up to the present time only a provisional significance. They 
have stood at best for imperfectly definable fragments, which were in 
some cases with difficulty distinguished from one another. Thanks to 
the newly discovered material, however, we know what the complete 
fish in at least two species besides Z. cuneatus was like, and the cranial 
osteology of ‘the larger one is as readily decipherable as that of a recent 
gar. In all, four species are recognized from ee American Eocene, and 
two from the Miocene, as follows : — 


L. atror Leidy (= L. anax Cope). Middle Eocene; Wyoming. 
L. simplex Leidy. Middle Eocene; Wyoming. 

L. notahihs Leidy. Eocene; Wyoming. 

L. (Clastes) cycliferus (Cope). Eocene; Wyoming. 

L. (Clastes) cuneatus (Cope). Miocene; Central Utah. 

L. (Pneumatosteus) nahunticus (Cope). Miocene; North Carolina. 


Turning to the European representatives of this family, we find only 
seven or eight species, likewise founded on fragmentary remains such as 
scales, vertebree, cranial fragments, etc., but nowhere a complete skeleton. 
The range is from Lower Eocene to Lower Miocene, and the distribution 
sparse in various localities of England, France, and Germany. With 
pardonable pride, therefore, we may point out that the specimen im- 
mediately to be described is at once the largest and most perfect fossil 


EASTMAN: FOSSIL LEPIDOSTEIDS. 69 


gar ever brought to light. It lacks any positively archaic features and 
bears close resemblance to living forms. It is obviously the direct 
progenitor of the modern Alligator gar, Z. tristechus (Bloch and 
Schneider), and compares with it very favorably both in size and general 
characters. But if we inquire into the more remote or pre-Eocene history 
of Lepidosteids, paleeontology gives us no answer. They blossom forth 
suddenly and fully differentiated at the dawn of the Tertiary without 
the least clue to their ancestry, unheralded and unaccompanied by any 
intermediate forms ; and they have remained essentially unchanged ever 
since. 


Lepidosteus atrox Lerpy. 
Plate 1, Fig. 2; Plate 2. 


1873. Lepidosteus atror Leidy, Proc. Acad. Nat. Sci. Phil., p78. 

1873. Lepidosteus atroxr Leidy, Rept. U. S. Geol. Surv. Territ., Vol. I, p. 189, 
Plate XXXII, Figs. 14,15. (Vertebre.) 

1873. Clastes atroxr Cope, Amn. Rept. U. S. Geol, Surv. Territ., 1872, p 634. 

1873. Clastes anax Cope, loc. cit., p. 659. 

1884. Clastes atror Cope, Rept. U. S. Geol. Surv. Territ., Vol. III, p. 54, Plate IT, 
Figs. 1-24. 

1884. Clastes anax Cope, loc. cit., p. 53, Plate IJ, Figs. 50-52. (Cranial bones.) 

1900. Lepidosteus atror Eastman, Geol. Mag. [4], Vol. VII, p. 57 


Definition. — A large species, equalling the recent Alligator gar in size and 
resembling it in general characters. Head contained about four times in total 
length; snout short and broad. External bones very heavy, ornamented with 
ramifying lines of ganoine tubercles which become consolidated into more or 
less radiating ridges on the operculum and suboperculum. Jaws with an outer 
series of numerous small teeth followed by a single series of large, regularly 
spaced, conical, striated teeth implanted vertically in a rather deep and narrow 
furrow. Dorsal and anal fins remote, nearly opposed ; caudal only slightly 
convex; pelvic situated about midway between the pectorals and anal. Dorsal 
fin-rays 8, caudal 12, anal 8, pelvic 6. Fulcra biserial and prominent on all 
fins. Scales very robust, in 18-20 longitudinal series, and between 50 and 60 
oblique transverse series counting along the lateral line. Surface of scales 
smooth or with feeble ornamentation, consisting of pittings and papille; 
posterior margin fimbriate, especially so in scales of abdominal region. 
Post-clavicular scales prominently sculptured. 

Preservation. — Except for the head, the specimen is very well preserved, 
and the fin-rays remarkably so. Two thirds of the fish, including the head, lies 
squarely on the ventral surface, but in the abdominal region the body is 
twisted, so that the right lateral aspect is exposed from the tip of the tail to a 
point midway between the anal and pelvic fins. The squamation is somewhat 


70 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 


disturbed anteriorly, scarcely at all so posterior to the line of flexure. All] the 
fins with the exception of the pectorals are beautifully preserved, but both 
pectorals are very defective. Notwithstanding the thickness of its separate 
plates, the cranial box yielded to pressure of the overlying matrix, and became 
irregularly flattened prior to fossilization. Most of the external head-bones are 
displaced, and the only ones escaping serious injury are the opercular apparatus 
and jaws of the right-hand side. The cranium, therefore, is in a very unsatis- 
factory condition for study, and it is fortunate our knowledge of its osteology 
is supplemented by a second specimen, which is described below. 

Cranwm, — Turning our attention first to the right-hand side of the head, 
we find that the operculum, suboperculum, interoperculum, preorbitals, maxil- 
lary and mandibular ramus all occupy their normal position with respect to 
one another, being simply flattened out, not displaced. The opercular plates 
have practically the same configuration and arrangement as in recent species, 
but are many times more massive, thus harmonizing with the powerful armor- 
ing of the trunk. The postero-inferior angle of the interoperculum is developed 
into a stout, blunt process overlapping the suboperculum. The latter plate, 
together with the operculum, has a slightly different ornamentation from the 
remaining bones of the head, in that the ganoine tubercles are fused into 
more or less continuous and radiating ridges. On the jaws and bones form- 
ing the roof of the head the tubercular ridges are ramifying and irregularly 
confluent, 

The maxillary is preserved in its entirety and measures 19 cm. in length. 
Anteriorly it shows a fontanelle as in recent forms, but traces of its segmenta- 
tion are now nearly obliterated. In the Washington cranium described by 
Mr. Lucas the segments are very distinct, and are seven in number. (See 
infra, p. 73). As the oral aspect of the maxillary is not exposed, nothing can 
be affirmed of its dentition. Considering its extreme narrowness, however, 
and the fact that only a single dental groove is opposed to it in the lower jaw, 
it is improbable that more than one series of large teeth was present. In this 
character a noteworthy difference is to be observed between the species under 
consideration and the recent L. tristechus (= L. viridis Gthr.), with which it 
stands otherwise in close agreement ; and incidentally it proves the artificial 
nature of Rafinesque’s subgenus Atractosteus. For if we emend the definition 
of the latter so as to include its nearest allied fossil species, no characters are 
left by which it can be distinguished from Lepidosteus s. str. Hence it seems 
best to discard altogether the subgeneric terms Atractosteus and Cylindrosteus.! 

The mandibular ramus is 25 em. long and composed of the usual parts, den- 
tary, angular, and coronoid. Immediately behind the last-named element are 
two circumorbital plates, but all the remaining circumorbitals and suborbitals 


1 According to Jordan and Evermann (Bull. 47, U. S. Nat. Mus., pt. 1, p. 109), 
“The name Litholepis, Rafinesque, applied by him to a gigantic gar, Litholepis ada- 
mantinus, the ‘Devil-jack Diamond Fish, is based on a drawing by Audubon, not 
intended by Audubon to represent any possible fish.” 


EASTMAN: FOSSIL LEPIDOSTEIDS. ri! 


are crushed into a confused mass. The outer rim of the dentary is set with 
a series of numerous minute teeth, next to which is placed a single series 
of large conical teeth implanted vertically in a narrow and moderately deep 
longitudinal groove. There are nine of these teeth spaced at regular intervals 
from the symphysis to about the middle of the lower jaw. They are of nearly 
uniform size, about 2 cm. in height, and vertically striated. Coronal cross- 
sections show the complicated structure of dentine characteristic of the genus. 
The symphysial teeth are directed forwards at a slight angle. The symphyses 
of both rami lie contiguous to one another in the limestone, but by far the 
greater portion of the left mandibular ramus and whole of the left maxillary 
are concealed by overlying bones. 

Next above the right maxillary lie a pair of long and narrow, deeply chan- 
nelled or folded elements, which presumably represent the palatines ; and 
adjacent to these are the median series of bones belonging to the cranial roof, 
which are now laterally displaced and very considerably injured. The oblique 
sutures between the frontals and ethmonasals are well shown, and also the 
sutures along the median line of the head. Premaxillaries and nasals are not 
preserved, and most of the bones belonging to the otic and occipital region are 
either missing or crushed beyond recognition. For this reason the length of 
the head in the median line cannot be accurately determined, although a con- 
servative estimate would place it at about 40cm. The distance in a straight 
line from the symphysis of the lower jaw to the posterior margin of the oper- 
culum is 45cm. The right and left clavicle are partially visible behind the 
head, but are in nowise remarkable either in size or configuration. 

Fins. — Very little remains of either of the pectorals, but all the remain- 
ing fins are beautifully preserved. The dorsal and anal are triangular, broad- 
based, and relatively high (20-22 cm.), with eight dermal rays each. These fins 
are very remote, and nearly opposed to each other. The caudal has a length 
of 24 cm., is composed of twelve finely articulated long rays and a lesser num- 
ber of short rays which differ from the rest in being uniserially articulated 
throughout their length. Prominent biserial fulera fringe the dorsal and 
ventral margins of the caudal and front margins of the remaining fins. The 
extreme tip of the tail is nof preserved, but it was apparently very slightly 
rounded. The pelvic fins are situated about midway between the pectorals and 
anal, and resemble the latter in form and size. 

The long proximal joints of each dermal ray in all the fins consist of two 
halves, or right and left portions, rather loosely united along the axial plane, 
and consequently subject to displacement. These proximal pieces correspond 
in number to the interneurals, which likewise have suffered some displacement 
in the dorsal and pelvic fins. Immediately after the proximal joint the rays in 
all fins become biserially articulated, and after a short interval become further 
bifurcated, much like the arms of crinoids. It will be seen from the following 
table that little variation in the radial formula exists amongst the various 
living and fossil species : — 


72 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 


SPECIES. RapiaL Formute. L SCALES OF 
ATERAL Line, 
L. atrox Leidy ID, (Ch We Ah. fe PAG. 50-60 
L. simplex Leidy IDB (Oo iYIs JN, 7 ce 2 circa 45 
L. tristechus (Bl. and Sch.) D.7-8; C. 12; A. 8; 125 (a5 60 
L. tropicus Gill DSi: Cpl AR Ce anGe 52-54 
L. platystomus Raf. DSi Fe Cl? ARS PG 56 
ZL. osseus (Linn.) ORR Oh ie ING Tee a 1B 62 


Scales. —The body armoring is excessively heavy, being on a par with that of 
the head, and recalling the powerful dermal defences of Lepidotus maximus trom 
the Upper Jura. In fact, these two species probably have the strongest scaly coat- 
ing of all fossil ganoids. Owing to flexure of the body in the present specimen, 
with consequent disturbance of the squamation anteriorly, it is difficult to count 
the longitudinal or even transverse scale-series with accuracy. There are no 
conspicuously marked scales along the dorsal ridge by which the median line 
of the back can be determined; but making all due allowance for displace- 
ment, the number of longitudinal series in the middle of the body may be set 
down at between 18 and 20, and of transverse oblique series counting along 
the lateral line at between 50 and 60. A very large anal scale marks the posi- 
tion of the vent. The exposed surface of most of the scales lying between the 
tail and middle of the body is smooth, but the posterior margin is strongly 
fimbriate. Some of the scales lying in advance of the pelvic fins are smooth, 
but the majority have their central portion ornamented with puncte, pittings, 
or channellings, and interspersed with these are occasional papilla. The lateral 
line in the present specimen is inconspicuously marked. To give enlarged 
figures of separate scales is hardly considered worth while, owing to the exten- 
sive series illustrated by Leidy and Cope. Those figured by Cope (Rept. U. 8. 
Geol. Surv. Territ., Vol. III. Plate II, Figures 8, 10-12) show the typical orna- 
mentation as well as any, and Figures 47 and 48 show the highly sculptured 
postclavicular plates. 

Vertebre. — The vertebral column is traceable for the greater portion of its 
length, although it protrudes only at intervals through the mass of scales so as 
to exhibit the individual centra. For views of detached vertebre reference 
must be had to the works of Leidy and Cope already cited. Stout displaced 
neural and hemal spines are visible in places along the extent of the vertebral 
column, and in some places ribs are to be distinguished. 

Coprolite. — Accompanying the specimen is a cylindrical coprolite 13.5 cm, 
long and 5.5 cm. in diameter, which is stated by the collector to have been 
found in close proximity to the fish. That it is of piscine origin admits of no 
doubt, and it could hardly have been voided by a smaller species than that 
under consideration. Its outer surface is marked with a few irregularly spiral 
folds, but is otherwise smooth. No large hard particles are to be distinguished, 
and the whole mass bears evidence of very thorough digestion. 


EASTMAN: FOSSIL LEPIDOSTEIDS. 73 


Regarding the fine head of Lepidosteus atrox (Plate 2) procured by Mr. 
Charles Schuchert for the United States National Museum while collecting in 
Wyoming last summer, Mr. Lucas writes : — 

“The specimen (Cat. No, 4755) consists of a little more than the anterior 
half of an individual of about the same size as that belonging to the Museum 
of Comparative Zoology at Cambridge. It lies upon the ventral surface, and 
while the body has of course been flattened, the cranium has suffered but little 
from compression, and is almost as favorable for study as a fresh gar would be. 

“The general form of the cranium is intermediate between that of Lepidos- 
teus osseus and L, tristechus, the muzzle being slightly wider than in the first- 
named and narrower than in the latter, so that there is no such obvious notch 
towards the anterior part of the ethmonasals as appears in L. tristechus. At 
the same time the back of the cranium is proportionately wider in the Eocene 
than in the living species, the result being that the skull of L. atrox tapers 
somewhat abruptly from behind forward. 

“The right vomer is turned outwards exposing its anterior end, and a frac- 
ture across the muzzle brings to view a section of the palatines ; from these 
exposures it is possible to state that both vomers and palatines are dentigerous, 
while in the lower jaw teeth are visible on the dentary. There is no apparent 
difference between the dentition of L. tristechus and L. atrox save that in the 
present specimen none of the teeth are so large as in the living species. The 
Cambridge example, however, shows this to be an individual peculiarity. Two 
nasal plates are present on either side as in existing gars, and the maxillary 
segments are seven in number, or one more than in the two examples of the 
Alligator gar available for comparison. The ethmonasals, especially the ex- 
ternal sculptured parts, are, as previously noted, narrower in L. atrox than in 
L. tristechus. The frontals are much the same in the two species, but the 
parietals and squamosals are a little shorter and wider in the fossil than in the 
living gar. The circumorbitals are displaced and few of them visible, but such 
as can be seen are notably thick. The same remark applies to the operculum 
and suboperculum, for although of practically the same size as in L. tristechus, 
they are decidedly thicker. The cranial bones ate also heavy, and their sculp- 
turing while well defined is a trifle finer and decidedly more granular.” 


PrincipAL MEASUREMENTS OF THE WASHINGTON Cranium (cf. Plate 2). 


Length from extreme tip of nasals to end of supratemporals . . . . 34.2 cm. 
Length of maxillary 4% o 6 6 6 6 6 Bo TURE 
Length of exposed portion of Dhnronaaal along Aine Bec rrn Camcums (1a) 
Length of frontals along median suture ........... .. 137 
lbengthvot parictalsyalongmediansuture 9.9... <<... . +. 46 
Waidtivacross anterior part of. ethmonasal 29.6294 «5°. 2... sO 
Width across exposed portion ofethmonasal . ........ =. «22 
Maximum width across anterior portion of both frontals . . .. . . 5. 
Maximum width across posterior portion of both frontals, at junction 

with squamosals .. . oS 


Maximum width between outer borders of niet ee left “quem elas 


74 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


Lepidosteus simplex Lerpy. 
Plate 1, Fig. 1. 


1875. Lepidosteus simplex Leidy, Proc. Acad. Nat. Sci. Phil., p. 73. 
1873. Lepidosteus simplex Leidy, Rept. U. S. Geol. Surv. Territ., Vol. 1, p. 191, 
Pl. XXXII, Figs. 18, 26, 31-43. (Vertebre, jaw-fragments, scales.) 


For the opportunity of describing this interesting specimen the writer is 
indebted to Mr. F. A. Lucas, who obtained possession of it in behalf of the 
United States National Museum after it had passed into oblivion since being 
exhibited by a private collector at the Chicago World’s Fair. It was ice 
originally at the typical Green River tess Wyoming, and bears the 
catalogue number 4754. 

The specific determination is based principally on scale characters, the 
enamel surface of the few detached scales known to Leidy being described by 
him as “ flat, smooth, and highly polished, and exhibits no markings except 
one or several minute puncte near the centre.”” One peculiar scale, which we 
can now recognize as belonging to the lateral line and oriented in a wrong 
position in Plate XXXII, Figure 33, of Leidy’s Monograph, is described (Rept. 
U.S. Geol. Surv. Territ., Vol. I, p. 191) as “traversed fore and aft by a canal 
communicating by a short cleft with the outer surface. The cleft is directed 
backward, and is protected by an angular elevation of the anterior border.” 
It would appear to be characteristic of this species that scales of the lateral line 
are traversed by short vertical canals instead of horizontal clefts, and the 
remaining scales are flat, smooth, and polished with entire edges. Other dis- - 
tinguishing features will be noted presently, and the definition may be emended 
as follows : — 

Definition. — A species attaining a total length of about 65 em., of which 
the head forms one fourth. External bones not especially heavy, arranged as 
in the recent Alligator gar, but with finer and more granular ornamentation ; 
the ganoine tubercles of operculum and suboperculum forming more or less 
continuous lines, as in L. atrox, but those of the interoperculum fused into 
irregular ridges. Jaws with an outer series of numerous small teeth followed 
by a single series of larger ones, the latter, however, relatively of much less 
size than in L. atroc. Vomers dentigerous, but no teeth observed on either 
palatines or parasphenoid. Fins as in ZL. atrox, but relatively weaker, and 
dorsal and anal more remote. Scales smooth and highly polished, with entire 
margins and no ornamentation save for occasional minute puncte near the 
centre; scales of the lateral line cleft by a short vertical canal. At least 45 
oblique transverse scale-series, and 18 to 20 longitudinal ones. Flank-scales 
of posterior part of the body considerably elongated in an antero-posterior 
direction. 

Description. —-The total length of the fish when straightened out was probably 
not far from 64 or 65 cm., or exactly four times the length of the head in the 
median line. In LZ. atroz and L. tropicus the head is also contained four times 


EASTMAN: FOSSIL LEPIDOSTEIDS. 75 


in the total length, in L. platystomus and L. tristechus three and one half, and 
in LZ. osseus with its specialized snout, but three times. The armoring of the 
present species is everywhere lighter and simpler than in the massive L. atroz, 
from which it is readily distinguished by its smooth scales with non-fimbriate 
posterior borders Another peculiarity which is probably of specific import- 
ance consists in the marked elongation of the flanked scales beginning with the 
series in advance of the anal fin and continuing to the tail. Many of the scales 
thus affected are twice as long as they are deep, which accounts for there being 
only 15 oblique transverse scale-series between the base of the tail and base of 
the anal fin, as compared with 21 such series in L. osseus, and 23 in L. trista- 
chus and L. atrox. Owing to flexure of the body with attendant disruption of 
the squamation, it is impossible to state accurately the number of oblique rows, 
but there were at least 45 of them, and possibly 50. 

The head appears to have been nearly severed from the body and turned 
completely over prior to fossilization, thus exposing the visceral surface to 
view. This was not accomplished without injury or displacement of certain 
parts, as witnessed by the position of the left palatine, which shows its oral 
surface adjacent to the right frontal (above in the figure), while the right man- 
dibular ramus, hyoid arches, and interoperculim are transported to the opposite 
side of the head (below in the figure). Back of the last-named element 
is seen from visceral aspect the left clavicle, a strong bone similar in all 
respects to that of recent gars. The interoperculum differs from the correspond- 
ing bone in L. atrox in. wanting a postero-inferior process, and it is relatively 
much lighter as well as somewhat smaller. Neither of the maxille are pre- 
served, and but one of the mandibular rami; this, the right-hand one, is 
turned downward so as to conceal most of the teeth, but the articular facets are 
well shown, and appear exactly as in L. tristechus. Little more can be said of 
the cranial bones, owing to their confused position and the fact that none of 
them differ in any appreciable respect from those of recent species. 

Of the vertebral column fourteen centra lying in natural order are visible back 
of the head, their length increasing rapidly from 0.55 cm., beginning with the 
first, to 0.85 cm. The fins are relatively weaker than in L. atroz, especially 
the caudal, which has fewer short rays , and the dorsal and anal are more 
remote. The radial formula is as follows: D. 7 (-8?); C. 12; A. 7 (-8?). 


TABLE OF MEASUREMENTS. 


Length of mandibularramus. .. . 5 6 oO. oo co UE Gm. 
Mens tbrofimberoperculumesee see ere al ae a OF 
Length of hypohyal ee ya Ot he eae eon 0S. 
lbenno Gaeiglnel 6 co 6 6 56 0 5 6 o goo o HS 
Length of epihyal Neen ase erst ae cei on tse is 2 LO 
saint or Gene ¢ 6 io () o be A) ceece (o eouecetc Mion ob 
Heirhtoticaudalipediclonwsele is) se | OO 
Width of basioccipital concavity . . . . . A sy otba dd le 


Distance from basioccipital concavity to vomer . . . . 16.0 


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4 


The following Publications of the Museum of Comparative Zoology 
are in preparation : — 


Reports on the Results of Dredging Operations in 1877, 1878, 1879, and 1880), in charge of ALEX- 
ANDER AGASSIZ, by the U. S. Coast Survey Steamer “ Blake,” as follows: — 


E. EHLERS. The Annelids of the ‘‘ Blake.” 

C. HARTLAUB. The Comatuls of the ‘* Blake,” with 15 Plates, 
H. LUDWIG. The Genus Pentacrinus. 

A. E. VERRILL. ‘The Aleyonaria of the “ Blake.” 


Illustrations of North American MAKINE INVERTEBRATES, from Drawings by BuRK- 
HARD, SONREL, and A. AGASSIZ, prepared under the direction of L. AGASSIZ. 


A AGASSIZ The Islands and Coral Rees of the South Seas .‘‘ Albatross’? Expedition 
of 1899-1900. 
LOUIS CABUOT. Immature State of the Odonata, Part 1V. 
E. L. MARK. Studies on Lepidosteus, continued. 
ne On Arachnactis. 
R. T, HILL. On the Geology of the Windward Islands. 
W. McM WOODWORTH. On the Bololo or Palolo of Fiji and Samoa. 
A. AGASSIZ and A. G. MAYER. ‘The Acalephs of the Ea>t Coast of the United States. 
A. G. MAYER. Some Acalephs from the South Paerfic. 
AGASSIZ and WHITMAN. Pelagic Fishes Part I1., with 14 Plates. 


Reports on the Results of the Expedition of 1891 of the U. S. Fish Commirsion Steamer 
“ Albatross,” Lieutenant Commander Z L. ‘TANNER, U.S. N., Commanding, in charge of 
ALEXANDER AGASSIZ, as follows : — 


A. AGASSIZ. The Pelagic Fauna. — J.P. McMURRICH. The Actinarians. 
: oe The Echini. E. L. MARK. Branchiocerianthus. 
e The Panamic Deep-Sea Fauna. JOHN MURRAY. ‘The Bottom Specimens. 
J. E. BENEDICT. The Annelids. ROBERT RIDGWAY. The Alcoholic Birds. 
K. BRANDT. The Sagittz. P. SCHIEMENZ. The Pteropods and Hete- 
WL The Thalassicola. ropods. 
C. CHUN. ‘The Siphonophores. W. PERCY SLADEN. The Starfishes. 
oe The Eyes of Deep-Sea Crustacea. L. STEJNEGER. The Reptiles. 
W H DALL. The Mollusks. THEO. STUDER. ‘The Alcyonarians. 
H. J. HANSEN. The Cirripeds. M. P. A. TRAUTSTEDT. The Salpide and 
W. A. HERDMAN. ‘The Ascidians. Doliolide. 
S$. J. HICKSON The Antipathids. E. P. VAN DUZEE. The Halobatida. 
W. E. HOYLE. ‘The Cephalopods. H. B. WARD. ‘The Sipunculids. 
G. VON KOCH. The Deep-Sea Corals. H. V. WILSON. The Sponges. 
C. A. KOFOID. Solenogaster. W. MoM. WOODWORTH. The Nemerteans. 


R. VON LENDENFELD. The Piospiio- 
rescent Organs of Fishes. 


- 


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OF THE 


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AT. HARVARD COLLEGE. 


There have been published of the BuLLetrys Vols. L to XXXY. 
of the Memoirs, Vols. I. to XXIV. 
Vols. XXXVE., 


_ original work by the Professors and Assistants of the Bcc . 
investigations carried on by students and others in the differen: 
Laboratories of Natural History, and of work by specialists based 
upon the Museum Collections and Explorations. 


The following publications are in preparation : — 


Reports on the Results of Dredging Operations from 1877 to 1880, in charge at 
Alexander Agassiz, by the U. S. Coast Survey Steamer “ Blake,” Lieut. : 
Commander ©. D. Sigsbee, U.S. N., and Commander J. R. Bartlett, Ue se N 
Commanding. 

Reports on the Results of the Expedition of 1891 of the U.S. Fish Coaninetite 
Steamer “ Albatross,” Lieut. Commander Z. I. tt peed U.S. Naas 
manding, in charge of Alexander Agassiz. . ea 

Contributions from the Beer ey Laboratory, in charge of Eieee E: ae 
Mark. é oe 

Contributions from the Geological bahoratorye in oleae of Protcue N. S. 
Shaler. : 5 z 

Studies from the Newport Marine Laboratory, communicated by Alexander — 
Agassiz. 2 ies 


Subscriptions for the ue of the Museum will be received Zs 
on the following terms : : ae 
For the 8utterm, $4.00 per volume, payable in advance. 
For the Menmorrs, $8.00 6s pis 8 = eee 
These publications are issued in numbers at irregular inter- 
vals; one volume of the Bulletin (8vo) and half a volume of the 2 
Memoirs (4to) usually appear annually. Each number of the Bul- | z 
letin and of the Memoirs is also sold separately. A price list & 
of the publications of the Museum will be sent on application _ cs 
to the Librarian of the Museum of Comparative Zoology, Cam- 
bridge, Mass. $e 


AES 


Bulletin of the Museum of Comparative Zovdlogy 
AT HARVARD COLLEGE, 
Vout. XXXVI. No. 4, 


CHARACTERS AND RELATIONS OF GALLINULOIDES, 
A FOSSIL GALLINACEOUS BIRD FROM THE 
GREEN RIVER SHALES OF WYOMING. 


By Freperic A. Lucas. 


Wirth One Puate. 


CAMBRIDGE, MASS, U.S. A.: 
PRINTED FOR THE MUSEUM. 
Avcust, 1900. 


Bulletin of the Museum of Comparative Zoology 
AT HARVARD COLLEGE. 
Vout. XXXVI. No. 4. 


CHARACTERS AND RELATIONS OF GALLINULOIDES, 
A FOSSIL GALLINACEOUS BIRD FROM THE 
GREEN RIVER SHALES OF WYOMING. 


3 


By Freperic A. Lucas. 


Wirs One Puate. 


CAMBRIDGE, MASS., U.S. A.: 
PRINTED FOR THE MUSEUM. 
Aveust, 1900. 


No. 4.— Characters and Relations of Gallinuloides wyomingensis 
Eastman, a Fossil Gallinaceous Bird from the Green River 
Shales of Wyoming. By Freperic A. Lucas. 


THE specimen upon which the following observations are based was 
discovered in the Green River Shales (Middle Eocene) of Fossil, 
Wyoming, during the summer of 1899, and was shortly after procured 
for the Museum of Comparative ZoGlogy at Cambridge, where it is now 
preserved (Cat. Foss. Birds, No. 1598). Dr. C. R. Eastman briefly 
described (Geological Magazine, February, 1900) the bird as Gallinu- 
loides wyomingensis, and at his solicitation a more detailed investigation 
of its structure and relations was undertaken, the results of which are 
herein set forth. 

Like the well-known Green River fishes, the specimen is very complete 
and in a most excellent state of preservation, although a little injured 
as to skull, vertebrae, and digits through the over-zealous preparation of 
the collector. There is a thin, dark, unctuous layer lying on the same 
plane as the skeleton and almost confluent with the thinner bones, so 
much so that in developing the finer points it was at times difficult to 
shun the temptation to carve out a character that might readily be 
imagined to exist. This layer obscures the ribs, which are scattered, as 
well as other portions of the skeleton. While, however, many structural 
details cannot be made out, the general characters are so distinct and 
the affinities of the bird so apparent that these defects are of compara- 
tively small importance. 

The Green River bird was of about the size of a Ruffed Grouse, but 
stood somewhat higher on its legs. Its galliform nature is obvious at a 
glance, the most apparent peculiarities being the length of the legs and 
the depth and the anterior extent of the sternal keel. The majority of 
its structural resemblances are with the curassows and with the genus 
Ortalis amongst those birds, but while according to Huxley’s definition 
it indisputably falls in the Peristeropodes, there are sufficiently strong 
characters to exclude it from both the Cracide and Megapodiide. The 
bird presents no points of affinity with any of the American grouse, still 
less with any of the Odontophorine. 

VOL. XXXVI.—NO. 4. 


80 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 


Cracine and Galline are herein used as short equivalents for “ peristero- 
podous ” and “ alectoropodous,” — the latter terms, although expressing 
the precise meaning needed, being a trifle cumbersome for ordinary use ; 
“galliform” is employed to designate such characters as are shared in 
common by all members of the Galliformes. 

Head. — The beak much resembles that of Ortalis, being moderate in 
size, stouter than in Crax, Rollulus, and Phasianus ; but not so short, 
stout, and decurved as in Colinus and allied genera. The holorhinal 
narial opening is also much like that of Ortalis, and the nasal, which has 
escaped injury, is typically galliform ; the superior process can be clearly 
seen, but the inferior process is covered on its lower part by crushed bone. 
The lachrymal, or prefrontal, appears to have been well developed, con- 
trasting in this respect with the American grouse (in which the prefron- 
tal is usually quite small), and agreeing with the curassows. The post- 
frontal process is stout and directed forwards. The mandible is stout 
and imperforate, and while it has a blunt angular projection, the re- 
curved process so characteristic of the Galliformes is lacking. This is 
the most notable departure from the galliform structure found in the 
skeleton. 

Vertebre and Ribs. — Little can be said of the vertebre save that the 
vertebral column presents the customary galliform arrangement of a free 
vertebra in front of the synsacrum preceded by a mass of anchylosed 
vertebre, but as to the number of the latter nothing can be affirmed. 
The cervicals have suffered from the mistaken zeal of the preparator, 
and but five can be definitely distinguished between what should be the 
axis and where the column disappears in the flattened bones of the 
wings. The caudals are mostly lacking, so that, unfortunately, nothing 
can be learned from them. 

Four pairs of ribs are articulated with the sternum, and at least one 
pair (one is the customary number in the Galliformes) arose from the 
synsacrum. Several ribs lie over the synsacrum, but there is no reason 
to suppose that all of them articulated with it. The usual number of 
ribs among the Galliformes is five on a side; Pavo has six, but the 
number in the present specimen cannot be made out. There is quite a 
little space between the first and second costal facets, the succeeding 
three being crowded together. This is interesting from the fact that it 
is a feature of modern galline birds, the spacing of the costals being 
more regular among the curassows. 

Shoulder Girdle. — The scapula is not unlike that of Rollulus, being 
long, narrow, and with parallel borders, as in many of the curassows, or 


LUCAS: GALLINULOIDES WYOMINGENSIS EASTMAN. 81 


as in Pediocetes. The coracoid resembles that of the Old World pheas- 
ants, and especially that of Phasianus colchius, more than it does the 
corresponding bone in any of the curassows. ‘The epicoracoid is a little 
more angular than is customary among Galliformes, but the epicoracoid 
of Pediocetes is of much the same pattern, and in this small point the 
Green River bird makes its nearest approach to some of the American 
grouse. The precoracoid process appears to be absent, as it is in most 
Galliformes, although there is a suggestion of this process in Arboriphila. 
The scapular process is small. The distal end of the coracoid makes a 
more obtuse angle with the shaft than is usual even in galline birds, 
but in this respect it is very similar to Phasianus colchius. 


Scapula, coracoid, and furcula, natural size. 


The furcula is unusually short and stout for a gallinaceous bird, ex- 
ceeding in this respect any species with which it has been compared ; it 
is U-shaped rather than V-shaped, most nearly resembling Numida in 
this particular. There is a distinct though slight acrocoracoid process, 
so that the furcula did not merely rest against the inner side of the 
coracoid, but articulated with it, thus differing from all existing Galli- 
formes. The scapular ends of the furcula are hidden so that it cannot be 
positively stated whether or not they reached the scapula. The hypo- 
cleidium is large and triangular, contrasting with Crax, which has a 
spinous hypocleidium, and exceeding Ortalis, in which this process is 
subtriangular and of moderate size. 

The sternum has a manubrium of moderate size, but from the disposi- 
tion of the bones it is impossible to ascertain whether it is perforate or 
imperforate. Both the external clefts are quite deep, and the external 
as well as internal xiphoid process is directed well backward ; both 


82 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 


processes are expanded at the free end. In the specimens of curassows 
available for comparison the external xiphoid is not pedate, but there is 
a suggestion of this condition in Talegallus. The sternal clefts are 
typically cracine, there being no approach to the deep internal cleft 
which makes the external and internal xiphoids of galline birds really 
branches of one process. The keel of the sternum is produced more 
anteriorly than in other Galliformes, though nearly approached by 
Centrocercus. It is to be noted that in this latter form the furcula is 
unusually long and narrow. 

Fore-limb. — The humerus, like the other bones of the wing, is stout 
and has the deltoid process well developed. The crushing which the 
bone has undergone prevents its being definitely stated whether or not 
the humerus was pneumatic, although the probabilities are that it was 
not. The structure of the wing, in conjunction with that of the sternum, 
indicates a bird of good powers of flight. The other bones of the wing 
lie so nearly over one another and are so flattened together that little can 
be said as to their details, save that the third metacarpal appears to 
have been much straighter than is usual among gallinaceous birds. 

Pelvie Girdle. — As the pelvis lies on its dorsal surface it cannot be 
stated whether or not it was eurved or straight in profile, but in the 
subequal proportions of the pre- and post-acetabular portions it resembles 
the curassows, although the conditions are much the same in Meleagris. 
It is somewhat wider in comparison with its length than in the curas- 
sows, the proportions resembling those observed in Thaumalea. There 
is no tendency toward separation of the ilia and ischia. The ischia do not 
seem to be bulged out to overhang the pubes as they do in Ortalis, but 
this feature is so extremely variable in the Galliformes as to have little 
or no significance. The pubes are long and slender, and as the speci- 
men now lies, they appear parallel with one another throughout their 
distal halves. In most Galliformes the pubes approach each other 
distally, sometimes, as in Ortalis and Penelope, being almost in contact. 
In this respect the Green River specimen departs from the cracine type 
and approaches such forms as Meleagris and Rollulus, and while it is of 
course possible that the pubes may have approached each other in the 
living bird, the intervening space is now so great as to make this seem 
doubtful. The prepubis is small, the obturator foramen very small, and 
the ilio-ischiadic space moderate. 

Hind-limb. — The femur is so crushed as to obscure its characters. 
There is no sign of a patella, though this may have been present. The 
cnemial ridges are slight, and there is the customary osseous tendinal 


LUCAS: GALLINULOIDES WYOMINGENSIS EASTMAN. 83 


bridge on the anterior face of the distal end of the tibia. The fibula is 
of the same general proportions as in other Galliformes. 

The hypotarsus is very likely only grooved, not perforate ; but this is 
one of the points that cannot be definitely ascertained without injury to 
thespecimen. ‘The number of tarsal tendinal perforations is a character 
of much importance in birds, for it seems fairly constant within the 
limits of a given large group and indicates the amount of specialization 
attained by the members of that group. As all Galliformes examined 
have a single tendinal perforation, the absence of such a character would 
indicate that our Eocene bird is of a more primitive type than its 
modern relatives. The usual tarsal sesamoid shows back of the right 
tarsal joint. The tarsus is longer in proportion to the tibia than in any 
other species examined, as is shown by the subjoined table, which gives 
the leugth of these bones in a few species : — 


SPECIES. LenGtH oF TIBIA. LENGTH OF TARSUS. Ratio. 
Gallinuloides wyomingensis 57° mm. 45° mm. 1.27 
Penelope superciliaris 115. 82. 1.40 
Rollulus roulroul 72. 48. 1.50 
Phasianus colchius 112. 12. 1.56 
Ortalis maccalli 108. 65. 1.66 
Colinus virginianus 53. 30. 1.77 


The toes are moderate and slender, of about the same length as those 
of Colinus virgintanus, but a little heavier ; yet they are not heavy in 
comparison with the size of the tarsus or the general bulk of the bird. 

The following table gives the length of the principal bones in the 
skeleton, all measurements being made in a straight line : — 


PrincipaAL MEASUREMENTS OF GALLINULOIDES WYOMINGENSIS. 


Occipital condyle to tip of bill, 47.°mm. Xiphoid to anterior end of keel, 59+ mm. 


Humerus, 47. Femur, 41. 
Ulna, 49 + Tibia, 67.+ 
Metacarpus, 25. Tarsus, 45. 
Scapula, 48. Basal phalanx of digit I, 7.5 
Coracoid, 29. do do do 16 il. 
Xiphoid to manubrium, 59. + do do do 1B ies 12. 
do do do DV: 7.5 


Relationships. — The various characters of the Green River bird may 
be summarized as follows : — 


84 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


Galline Characters. — Pedate end of internal xiphoid process, arrange- 
ment of the costal facets, and shape of the distal end of coracoid. ; 

Cracine Characters. — Blunt, upright, subtriangular costal process, 
shallow inner sternal notch, small prepubis, proportions of pelvis, elon- 
gate tarsus with all the toes on the same level. 

Peculiar Characters. — Absence of recurved mandibular process ; 
short, stout, U-shaped furcula with large hypocleidium and articular 
facet for coracoid. 

The weight of the peculiar characters, particularly the absence of a 
post-angular process, are, as stated in the introductory remarks, sufficient 
to prevent the bird being placed in either the Cracide or Megapodide, 
thus necessitating the establishment of a new family, Gallinuloidide. 
The principal family characters are the absence of a postangular man- 
dibular process, presence of an articular facet on the furcula for the re- 
ception of the acrocoracoid, and the presence of an acrocoracvid. 

The generic characters are considered to be the stout U-shaped 
furcula, the shape of the scapula, and the anterior extent of the crista 
sternt, As specific characters are always comparative, none can be 
formulated from a single specimen, even did they not depend to so great 
an extent in birds — often entirely — on external features. 

This bird is interesting not because it presents any striking peculiari- 
ties of structure, but rather because it does not, and because it belongs, 
as we might naturally expect from its age, to a generalized type having 
points of structural resemblance with various families of gallinaceous 
birds. It is an additional reminder, were any needed, of the great gaps 
in our knowledge of the development of birds and of the rapidity with 
which they attained their present forms. The mammals of the Eocene 
are quite different from existing species, but this bird readily takes its 
place among the forms of to-day. 


I. 


rLAIE 


= 
| 


BOSTON. 


THE HELIOTYPE PRINTING CO. 


- 


iv 


The following Publications of the Museum of Comparative Zoolog 
are in preparation : — 


Reports on the Results of Dredging Operations in 1877, 1878, 1879, and 1880, in charge of ALEX- 
“ANDER AGASSIZ, by the U. S. Coast Survey Steamer “ Blake,” as follows: — 


E. EHLERS. The Annelids of the ‘‘ Blake.” 

CG. HARTLAUB. The Comatuls of the ‘ Blake,” with 15 Plates, 
H. LUDWIG. The Genus Pentacrinus. 

A. BE. VERRILL. ‘he Alcyonaria of the “ Blake.” 


Illustrations of North American MARINE INVERTEBRATES, from Drawings by Burk- 
HARD, SONREL, and A. AGASSIZ, prepared under the direction of L. AGASsIZz. 


A. AGASSIZ. The Islands and Coral Reels of the South Seas. 
of 1899-1900. 
LOUIS CABOT. Immature State of the Odonata, Part 1V. 
E. L. MARK. Studies on Lepidosteus, continued. 
Se On Arachnactis. 
R. T, HILL. On the Geology of the Windward Islands. 
W. McM. WOODWORTH. On the Bololo or Palolo of Fiji and Samoa. 
A. AGASSIZ and A. G. MAYER. The Acalephs of the East Coast of the United States, 
A. G. MAYER. Some Acalephs from the South Pacific. 
AGASSIZ and WHITMAN. Pelagic Fishes. Part II., with 14 Plates. 


** Albatross’? Expedition 


Reports on the Results of the Expedition of 1891 of the U. S, Fish Commission Steamer 
“ Albatross,” Lieutenant Commander Z. L. TANNER, U.S. N., Commanding, in charge of 
ALEXANDER AGASSIZ, as follows: — 


A. AGASSIZ. The Pelagic Fauna. J.P. McMURRICH. The Actinarians. 
* The Echini. E. L. MARK. Branchiocerianthus. 
* The Panamic Deep-Sea Fauna. JOHN MURRAY. ‘The Bottom Specimens. 


J. E. BENEDICT. The Annelids. 
K, BRANDT. The Sagittz. 
Oo; The Thalassicolz. 


C. CHUN. ‘The Siphonophores. 
KS. The Eyes of Deep-Sea Crustacea. 
W. H. DALL. The Mollusks. ‘ 


Wi. J. HANSEN. The Cirripeds. 

W. A. HERDMAN. ‘The Ascidians. 

S. J. HICKSON. The Antipathids. 

W. E. HOYLE. ‘The Cephalopods. 

G. VON KOCH. The Deep-Sea Corals. 

C. A. KOFOLD. Solenogaster. 

R, VON LENDENFELD, ‘The Piiospho- 
rescent Organs of Fishes. 


ROBERT RIDGWAY. ‘The Alcoholic Birds. 

P. SCHIEMENZ. ‘The Pteropods and Hete- 
ropods. ; 

W. PERCY SLADEN. The Starfishes. 

L. STEJNEGER. The Reptiles. 

THEO. STUDER. ‘The Alcyonarians. 

M. P. A. TRAUTSTEDT. The Salpide and 


Doliolidz. 
E. P. VAN DUZEE. ‘The Halobatide. 
H. B. WARD. ‘The Sipunculids. 


H. V. WILSON. The Sponges. 
W. McM. WOODWORTH. The Nemerteans. 


PUBLICATIONS 


OF THE 


MUSEUM OF COMPARATIVE ZOOLOGY 


AT HARVARD COLLEGE. & 


There have been published of the BuLLettns Vols. I. to XXXV.; ; 
of the Memoirs, Vols. I. to XXIV. 


Vols. XX:XVI., XXXVII., and XXXVIII. of. the BuLierin, 


and Vol. XXV. of the Memos, are now in course of publication. 


The Butterin and Memoirs are devoted to the publication of 


original work by the Professors and Assistants of the Museum, of - 


investigations carried on by students and others in the different 


Laboratories of Natural History, and of work by specialists based — ) 


upon the Museum Collections and E xplorations. 


The following publications are in preparation : — 


Reports on the Results of Dredging Operations from 1877 to 1880, in charge of 
Alexander Agassiz, by the U. S. Coast Survey Steamer “ Blake,” Lieut. 
Commander C. D. Sigsbee, U. S. N., and Conparsndce J. R. Bartlett, U.S.N., 
Commanding. 

Reports on the Results of the Expedition of 1891 of AE U.S. Fish Commission 


Steamer “ Albatross,” Lieut. Commander Z. L. Tanner, U. S. N., Com- 


manding, in charge. of Alexander Agassiz. 

Contributions from the Zodlogical Laboratory, in charge of Professor E. 7 
Mark. 

Contributions from the Geological Laboratory, in charge of Professor N. S. 
Shaler. 

Studies from the Newport Marine Laboratory, communicated by Alexandee 
Agassiz. 


Subscriptions for the ese of the Museum will be received 
on the following terms : 


For the Butierrin, $4.00 per volume, payable in advance. 
For the Mrmorrs, $8.00 ee ee a 


~ 


These publications are issued in numbers at irregular inter- 
vals; one volume of the Bulletin (8vo) and half a volume of the 
Memoirs (4to) usually appear annually. Each number of the Bul- 
letin and of the Memoirs is also sold separately. A price list 
of the publications of the Museum will be sent on application 
to the Librarian of the Museum of Comparative Zodlogy, Cam- 
bridge, Mass. 


rs, 


ea 
os od 


4 


oe 2 iG 
EVELOPMENT. CP | TARY CEE SERS or 
_ANURIDA arr uel HINSS 


27h rth 


Wirt Ercut Piates. 


CAMBRIDGE, MASS., U.S. A.:. 
PRINTED FOR THE MUSEUM. 


Octoser, 1900. 
sa Tey. Hs 


2 


ete ein ‘ 
— MMO MOR KG cot 


4 


Gh Ade 


(if 


Bulletin of the Museum of Comparative Zoology 
AT HARVARD COLLEGE. 
VoL. XXXVI_- No. 5. 


THE DEVELOPMENT OF THE MOUTH-PARTS OF 
ANURIDA MARITIMA GUER. 


By Justus Watson Fo.usom. 


Wits Ereut PLATES. 


CAMBRIDGE, MASS., U.S.A.: 
PRINTED FOR THE MUSEUM. 


OctoBER, 1900. 


OCT 30 1900 


No. 5.— The Development of the Mouth-Parts of Anurida 
maritima Guer4 By Justus Watson FoLsom. 


CONTENTS. 

PAGE PAGE 
Introduction ... . . . . . 87|Linguaand Superlingue .... 110 
WeTHOUSH mE een cs oe ts er) So Maxiller 5 08a) cet ber oe ie ALD 
General Description of Egg . . . 89|Labium .........~. 126 
Rane Singers 2 ¢ o 6 o a GWHISOIIl. 696 g56 G56 6 Ga o WS 
Procephalic Lobes . . . , . . Q91}]Tentorium.. . 6 6 9 TEY 
Labrum and Clypeus . . . . . 93} Segmentation of the Head Eee Uy 
Antenne . o @ of olism, 6 oe 6 62a og o o Tels 
Dremandibular’ Appendages s o o CbBiiieareNNy 6 of 6 5 6 o 6 co I 
Mandibles . . . ve 02) |) Explanationiof Plates sncmsen san elon 

Introduction, 


Our present ideas of homology in the details of insect mouth-parts 
rest almost exclusively upon anatomical data, and need careful revision 
in the light of embryological facts. 

Too many entomologists have speculated upon the subject in complete 
disregard of evidence from ontogeny or phylogeny. Embryologists, on 
the other hand, have greatly neglected the mouth-parts. 

It seems almost superfluous to insist that highly specialized organs 
can be but imperfectly understood unless studied in egg and larva as 
well as imago ; that generalized types illuminate specialized forms ; and 
that equivalent groups are linked together through their more general- 
ized members ; yet too often these accepted principles are not applied. 

The objects ‘of the present paper are two: first, to supplement my pre- 
vious account (Folsom, ’99) of the anatomy and functions of the mouth- 
parts of a representative Collembolan ; second, to discuss the morphology 
of mandibulate mouth-parts of insects and their nearest allies upon 
anatomical and embryological evidence derived from the most primitive 
insects, the Apterygota. 

1 Contributions from the Zodlogical Laboratory of the Museum of Comparative 


Zoviogy at Harvard College, E. L. Mark, Director, No. 114. 
VOL. xxxvi.— No. 5 


88 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


My comparisons have been hindered by the scanty and fragmentary 
nature of published embryological observations upon the mouth-parts of 
Arthropods. Detailed studies upon the subject in the less specialized 
Pterygota, Crustacea, Arachnida, Diplopoda, and Chilopoda do not exist, 
but are necessary for the proper understanding of the morphology of the 
mouth-parts, and will have much bearing upon the phylogeny of the 
classes named. 

The present study was made under the supervision of Dr. C. B. Daven- 
port, to whom I am most grateful for his constant, critical supervision, 
valuable advice and encouragement. 

Professor E. L. Mark has carefully revised the text and attended to 
all the details of publication ; his help, as always, has been of inestimable 
value to me. 


Methods. 


For killing eggs, and adults as well, simply hot water was used, with 
excellent results. After killing, material was carried through several 
successively stronger grades of alcohol and finally preserved in absolute 
alcohol. 

In the study of the embryo, both dissections and serial sections were 
made. As much as possible was learned by dissection, as that method, 
although difficult, gave more trustworthy results than could possibly be 
obtained by reconstruction from sections. The germ bands of freshly 
killed embryos were too delicate to be dissected out uninjured ; but after 
being in absolute alcohol for two months they had become sufficiently 
hardened for this operation. A longer stay made them brittle, but 
advantageously so in some respects. 

Dissections were made under a compound microscope with a magnifi- 
cation of about one hundred and fifty diameters. For the finest work, 
the ‘‘minutien Nadeln,” used by entomologists for pinning minute in- 
sects, were employed. The general form and position of an embryo 
could be seen through the transparent egg-membranes; but to get 
clearer views, the outer membrane was removed, the remaining corru- 
gated membrane punctured, and a staining fluid allowed to penetrate 
the germ band. Preparatory to the dissection of minute structures, the 
egg was placed in weak glycerine, which caused the embryo to shrink 
away from the membranes slightly, allowing these to be removed ; the 
germ band was dissected out and stained with Grenacher’s alcoholic 
borax-carmine or hematoxylin. Isolated parts of the embryo were 
mounted temporarily in weak glycerine without pressure, in such a 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 89 


way that by moving the cover glass they could be rolled into various 
desirable positions. 

For sectioning, portions of the embryo, or punctured eggs, were im- 
bedded in hard paraffine. The eggs required at least four hours for 
thorough penetration. For orienting, Woodworth’s (’93) method was 
employed, but not always with success, as the objects were liable to be- 
come distorted or even lost. A simpler, but more efficient, method for 
these particular objects was to orient them under the compound micro- 
scope with a hot needle in a glycerine-smeared watch-glass of melted 
paraffine, and to fix them in place by touching the glass beneath with 
cold water before hardening the paraffine throughout. When the block 
of paraffine was inverted under the compound microscope, the imbedded 
object could be seen through a thin film of paraffine, and a scratch could 
be made to indicate the plane of sectioning. 

Sections from 5 to 10 w in thickness were cut with either a Reichert 
or a Minot-Zimmermann microtome, fastened with Mayer’s albumen 
mixture, and stained with various reagents, chiefly Delafield’s or Klein- 
enberg’s hematoxylin followed by safranin, Grenacher’s alcoholic borax- 
carmine, and Heidenhain’s iron-hematoxylin. 


General Description of Egg. 


The eggs of Anurida maritima are spherical, from 0.26 mm. to 
0.38 mm. in diameter, enlarging with age, and at first light yellow, 
later becoming orange. 

They occur abundantly along the Atlantic coast under stones between 
tide-marks, and are usually mingled with the conspicuous white exuvice 
of the parents. 

The eggs of Collembola depart widely from those of other insects by 
being holoblastic; they are slightly unequal in cleavage. After the mo- 
rula stage the outer nuclei and accompanying protoplasm migrate toward 
the periphery, leaving behind yolk masses and also cells which subse- 
quently prove to be entodermal. The peripheral cells become arranged 
in two layers: the ectoderm, a continuous superficial layer, with nuclei 
at regular intervals, and the mesoderm, an inner, less compact layer 
with fewer and scattered nuclei. Thus there soon results a condition 
like that derived from superficial cleavage. The ventral plate, or germ 
band, is formed by migrant mesoderm cells, and, according to Uzel (98, 
p- 22, Tomocerus), is first represented by two pairs of isolated thicken- 
ings, —the procephalic and mandibular fundaments. I have found 


90 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


that the appendages appear in succession from in front backward, and 
that they are well developed long before the segmentation of the germ 
band. The blastoderm is interrupted only by the “ dorsal organ,” 
which is attached to the inner egg membrane. 

Claypole (98, pp. 255-258) distinguishes five egg membranes in 
Anurida, and maintains that all arise from the egg or the blastoderm. 
I find that in the ripe egg two are evident: a thick outer and a thin 
corrugated inner one, respectively analogous to, if not homologous with, 
the chorion and the vitelline membrane of other insects. Another deli- 
cate membrane completely envelops the embryo in early stages (Plate 1, 
Figures 1, 3, mb.), except where interrupted by the dorsal organ. I have 
found it to be, not a “ larval skin,” but a blastodermic membrane. 

The peculiar cleavage of Collembola has been observed by Oulganine 
(75, 76), Lemoine (83), Claypole (98), and Uzel (98). In the most 
nearly related group, Thysanura, the cleavage has been shown to be 
superficial by Grassi (85), Heymons (’96, ’97°), and Uzel (97, 98). 
In cleavage, then, Collembola resemble many Crustacea and Arachnida, 
in which it is at first total and secondarily superficial. 

Thysanura, on the other hand, approach the Orthoptera, in that the 
cleavage is from the first superficial. 

The “dorsal” or “ precephalic” organ of Collembola has been de- 
scribed by Lemoine (’82), Wheeler (93), Claypole (98), and Uzel (’97, 
98) ; of Thysanura, by Grassi (85), Heymons (96, ’97°), and Uzel 
(97,98). Wheeler homologized it with the “indusium ” of Orthoptera, 
and suggested its analogy with the embryonic sucking-disk of Clepsine. 
Claypole collected evidence of a similar structure in Crustacea, which 
has been reinforced by Uzel. 


Reference Stages. 


For descriptive purposes I have selected nine consecutive stages of 
development, which may be identified in the entire egg by the following 
characteristics : — 

At Stage 1 (Plate 1, Figure 1) the embryo is almost spherical with 
all the primary appendages represented by small papille. The dorsal 
organ is large, with a spherical imbedded portion and an expanded super- 
ficial part, the latter firmly attached to the corrugated membrane. This 
stage is very nearly that of Claypole’s (98, Plate XXIII.) Figures 40 
and 41 of the same species. 

Stage 2 (Plate 1, Figure 2) is characterized by folds representing the 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 91 


last five abdominal segments, and by longer appendages, of which the 
antenne and legs show traces of segmentation. It is approximately 
the stage of Figures 42 and 47 of Claypole. 

At Stage 3 (Plate 1, Figure 3) the ventral surface of the embryo is 
almost flat, preparatory to involution; the legs are decidedly longer, 
and the fundament of the proctodzum is distinct. Figures 43 and 
43° of Claypole belong near this stage ; also Figure 10 of Ryder (’86), 
likewise for Anurida maritima. 

During Stage 4 (Plate 1, Figure 4) the germ band is folding into the 
yolk, the fold beginning anteriorly and continuing backward. The 
antenne and legs are long and stout. My figure shows a stage a little 
later than that of Figure 44 by Claypole. 

At Stage 5 (Plate 1, Figure 5) the involution has reached the centre 
of the egg, the antennz and legs are distinctly segmented, the mouth- 
folds are conspicuous, and the dorsal organ has shrunken considerably. 

Stage 6 (Plate 1, Figure 6) is much like the last, except that the 
head and tail of the embryo have approached each other. The dorsal 
organ is much reduced and somewhat flask-shaped. This is the stage 
of Ryder’s Figure 7. 

At Stage 7 (Plate 2, Figure 7) the eyes are first recognizable as five 
black circular patches on either side. Figure 45 of Claypole represents 
this condition. 

Stage 8, which I have not figured, differs externally from the last in 
that the number of eyes is no longer evident, it being obscured by a 
suffusion of pigment. The degenerating dorsal organ now disappears by 
resorption. 

Stage 9 (Plate 6, Figure 41; also Claypole, Figure 48) refers to the 
newly hatched insect. Before this period, movements of the insect may 
be seen through the egg membranes. If eggs have been kept dark, — 
the normal condition, — the emerging insects are white, excepting the 
eyes ; if exposed to sunlight, however, the embryos become blackish- 
blue long before hatching. At emergence the external clothing of setz 
is complete, and the mouth-parts are fully formed. 


Procephalic Lobes. 


The fundaments of the procephalic lobes are two isolated thickenings 
of the blastoderm, which are the first of the paired fundaments to ap- 
pear. Each procephalic fundament is lenticular in form and rapidly 
increases in thickness and area. In the earlier stages the procephalic 


92 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


thickenings are not definitely circumscribed, but merge insensibly with 
the rest of the blastoderm. 

Previous to Stage 1 the procephalic lobes meet in the median plane, 
where the labral fundament then appears. Before the appearance of 
the labrum, however, the antennal fundaments evaginate from the pos- 
terior regions of the procephalic lobes. 

In Stages 1 and 2 (Plate 1, Figures 1 and 2) the lobes continue to 
increase in area and thickness. 

At Stage 3 either lobe is relatively as thick as is represented in 
Figure 3, pr’ceb., and in lateral surface views (Plate 2, Figures 9, 10, 
pr'ceb.) appears as a strongly convex, oval protuberance. 

In Stages 4 (Plate 3, Figure 12, pr’ceb.) and 5 (Plate 3, Figures 19, 20, 
21, pr’ceb.) the procephalic lobes change little except in size, and the 
median depression between them (sz/.) is still distinct. 

In Stage 7 (Plate 5, Figure 30) the depression (sw/.) becomes obliter- 
ated, and the eyes (Plate 4, Figure 24, ocl.) and postantennal organs 
(Figure 24, o.p’at.) appear. At this stage sections show a pair of gan- 
glionic fundaments (Plate 4, Figure 28, pr’ceb.), the largest and most 
anterior in the head, with which the next two pairs eventually unite to 
form the supra-cesophageal ganglion of the adult (Plate 8, Figure 51, 
gn.swe@.). 

In other Collembola the procephalic lobes develop in just the same 
way, as may be gathered from Nicolet (42, Smynthurus), Packard (’71, 
Isotoma), Lemoine (’83, Smynthurus), and Uzel (98, Tomocerus). 

Also in Campodea the same course of development is followed (Uzel, 
’98, Taf. 3, Figures 33-36; Taf. 4, Figures 37-42) as well as in Lepis- 
ma (Heymons, 797°). 

In fact, the simple process described for Anurida characterizes not 
only Orthoptera (Ayers, ’84, Wheeler, 793, Heymons, ’95), but also in- 
sects in general. 

The procephalie lobes of Diplopods and Chilopods develop essentially 
as in insects and Crustacea, but no detailed comparisons can be made 
as yet. 

The most interesting considerations concerning the ocular segment of 
Hexapoda relate to its equivalence with the first segment of Crustacea. 

Viallanes (’87, pp. 98-109) has carefully compared the brain in both 
classes and found a striking agreement, extending to histological details : 

‘¢Considérons en premier lieu la partie latérale du protocérébron, 
connue des anatomistes sous le nom de ganglion optique; elle nous montre 
d’abord, en allant de dehors en dedans, les parties suivantes: les fibres 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 93 


post-rétinennes, la lame ganglionnaire, le chiasma externe, la masse 
médullaire externe, le chiasma interne et la masse médullaire interne. 

“Toutes ces parties, si nettement caractérisées, se retrouvent sans 
modification chez |’Insecte; il n’est done pas douteux qu’il existe au 
moins pour cette premiére région du ganglion optique similitude com- 
pléte entre les deux types que nous cherchons a4 comparer. . . . Cette 
similitude a été reconnue par tous ceux qui se sont occupés de ce sujet 
(Berger, Bellonci, Carriére et moi)... . . En somme, au point de vue 
des parties dont nous venons de parler, il n’existe que des différences 
bien peu importantes entre l’Insecte et le Crustacé: chez le premier, les 
deux lobes cérébraux sont trés rapprochés et se soudent sur la ligne 
médiane ; chez le second, ces mémes parties (appelées balles supérieures) 
sont écartées, chacune d’elles étant logée dans le pédoncule oculifére 
correspondant.” 

Packard ’98, p. 51) says, “Hence the ocular segment, 7. ¢, that 
bearing the compound and simple eyes, is supposed to represent the first 
segment of the head. This, however, does not involve the conclusion 
that the eyes are the homologues of the limbs, however it may be in 
the Crustacea.’’ As Viallanes has proved the equivalence of protocere- 
brum and optic nerves in insects with those of Crustacea, and others 
have shown that the compound eyes of both groups are constructed 
alike, even to the number of retinal elements, it is proper to infer that 
the compound eyes of the two groups are homologous. 

The protocerebrum of Collembola and Thysanura agrees in develop- 
ment and structure with that of other insects and also with decapod 
Crustacea ; the facetted eyes of Hexapoda and Crustacea are likewise 
homologous. 


Labrum and Clypeus. 


The labrum is chiefly interesting because it has frequently been held 
to represent a pair of primary appendages. 

At Stage 1 (Plate 1, Figure 1; Plate 2, Figures 8, 8%, lbr.) the 
labrum (really clypeo-labrum) is a median hemispherical papilla anterior 
to and distant from the bases of the antennz ; at no period does it give 
evidence of a paired origin. 

At Stage 2 (Figure 2), while the distances between the labrum and 
mandibles is precisely the same as in the preceding stages, the antennz 
are inserted beside the oral region of the upper lip; the latter is globular 
and flattened against the egg shell. 


94 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


Surface views at Stage 3 (Figure 3) are given in Figures 9, 10, and 
LS dor: 

A sagittal section at this stage shows (Plate 3, Figure 13) an elon- 
gation of the labral fundament, and demonstrates its origin from the 
germ band by simple evagination. The posterior surface of the labrum 
is now the anterior wall of a distinct invagination (or.), the fundament 
of the stomodzeum. 

At Stage 4 (Figure 4) the labrum is longer (Plate 3, Figure 19, dbr.) 
and its long axis has swung backward, probably on account of the ex- 
cessive elongation of the anterior labral surface. A ventral aspect of 
the germ band (Figure 12) shows the labrum to be approximately oval 
in cross-section, but with a more rounded anterior surface. 

At Stage 5 (Figure 5) the labrum (Plate 3, Figure 20, br.) is de- 
cidedly longer. The basal part of the labral fundament represents the 
clypeus, with which the lateral folds, or mouth-folds (Figure 21, pli.or.) 
are now confluent ; overhung by the end of the labrum is the distinct 
stomodzeum. 

At Stage 7 (Figure 7) a distinct depression (Plate 5, Figure 31, dep.) 
separates the clypeus from the procephalic lobes ; the depression, in 
fact, may be seen as early as Stage 1, for it simply forms the angle be- 
tween the labral fundament and the procephalic lobes. Although the 
clypeus merges insensibly into the cheeks, the labrum is a free trapezoi- 
dal plate, as in the adult (Plate 6, Figure 40, dbr.). The antenne are 
now iuserted (Plate 4, Figure 24, Plate 5, Figure 30, at.) almost ex- 
actly opposite the base of the labrum. At this stage the clypeo-labral 
suture is not distinctly indicated (Figure 24), but in Stage 8 an invagi- 
nation occurs to form the labral hinge of the adult (Plate 6, Figure 40, 
ate.). 

In Stage 8 the only other important changes in the labrum are the 
evagination of single hypodermis cells to form the external sete, and 
the formation of trivial cuticular folds which represent the rudiments 
of the epipharynx. In Anurida, as in Orchesella, the epipharynx is 
purely a cuticular structure and unconnected with the central nervous 
system. 

In the adult Anurida a shallow clypeo-frontal groove is distinguish- 
able (Plate 6, Figure 40, su/.), but does not amount to a suture, and 
the clypeus is not laterally demarcated from the groove. In Orchesella 
and Tomocerus, however, the clypeus is a distinct sclerite. In none of 
the Collembola that I have studied is there any distinction between 
clypeus and labrum on the roof of the pharynx. 


—— 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 95 


Packard (’71, p. 18) says, regarding Isotoma, “‘ The clypeus, however, 
is merged with the epicranium, and the usual suture between them does 
not appear distinctly in after life, though its place is seen in Figure 13 to 
be indicated by a slight indentation. The labrum is distinctly defined 
by a well-marked suture, and forms a squarish knot-like protuberance, and 
in size is quite large compared to the clypeus. From this time begins 
the process of degradation, when the insect assumes its Thysanurous 
characters, which consist in an approach to the form of the Myriapodous 
head, the front, or clypeal region being reduced to a minimum, and the 
antenn and eyes brought in closer proximity to the mouth than in 
other insects.” 

Lemoine (’83, p. 510, Planche XV., Figure 24) mentions in Smynthu- 
rus, “ Les deux appendices qui constitueront la lévre supérieure,” but 
they appear in his figure as only simple lobes from a large, median 
labrum. 

Wheeler (’93, p. 57, Figure VI.) represents the labrum of Anurida as 
a median, unpaired fundament, and Claypole (’98, Plate XXIII.) gives 
several surface views of the upper lip in the same species. 

Uzel (98, Taf. VI., Figur 87) shows the single labral fundament of 
Macrotoma (Tomocerus). 

Regarding Campodea, Uzel (98, p. 26) says: “‘ Vor der Mundeinsen- 
kung erblickt man jetzt schon die unpaare Anlage der Oberlippe,” and 
partially illustrates (Taf. IV., VI.) the development, which proceeds 
essentially as in Anurida. 

The finished labra of Campodea (Grassi, ’86°, Tay. IV., Figura 7) and 
Japyx (Grassi, ’86°, Tay. II., Figura 15 62s) are very simple rounded 
plates. 

For Lepisma, Heymons (’97°, Taf. XXX.) figures the labral funda- 
ment as a prolongation from the procephalic lobes, and characterizes it 
(p. 591) as “eine kleine, vollkommen, ungetheilte, einfache Platte.” 
Later (p. 593) he says, “ Die Oberlippe wird bedeutend grésser und 
bekommt an ihrem hinteren Rande eine mediane Einkerbung (Figure 17).” 
The median indentation is clearly, however, a secondary formation. 

In both Lepisma and Machilis (Oudemans, ’88, Taf. I., Figur 3) the 
labrum remains simply an anteriorly rounded plate. 

In the Orthopteran CEicanthus, Ayers (’84, p. 240, Plate 18, Figures . 
21, 22) describes the unpaired fundament which forms the ovate labrum. 
In short, the labrum in all Orthopteran families develops from an un- 
paired fundament. (See Wheeler, ’93, Heymons, 795°.) 

The same is true of the Libellulide and Ephemeride (Heymons, ’96, 


96 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


Taf. II., Figuren 19, 29), and examples might be multiplied to show 
that the labrum does not represent a pair of appendages. The view 
held by Kowalevsky, Carriere and others, that it did, was based chiefly 
upon anatomical evidence, which has since been disproved by Heymons 
(95) and others. (See Packard, ’98, pp. 42-43.) 

Scolopendrella (Latzel, 84, p. 8, Taf. I., Figur 4; Grassi, ’86%, p. 15, 
Tav. IL., Figura 6) has a simple, emarginate, six-toothed labrum, and, 
like Hexapoda, a distinct, subtriangular clypeus. Moreoyer, as Packard 
(98, p. 22) has affirmed, it has a V-shaped tergal suture, which exists 
also in the more generalized insects, but is absent in Myriopods. 

In Diplopoda, an upper lip is present as a transverse plate, fused, 
however, with the cranium. 

In Chilopoda, a similar labrum is present, but is not always basally 
fused, and frequently consists of three transversely placed sclerites. It 
originates as a simple median lobe (Heymons, ’97°, p. 4, Figur 1, Scolo- 
pendra). 

In Crustacea the upper lip is derived from a median, unpaired evagi- 
nation corresponding almost exactly in position with the labral funda- 
ment among insects. 

Among insects, then, the labrum and clypeus develop from a median 
evagination between the procephalic lobes, and give no satisfactory evi- 
dence of paired origin. The same statement applies also to Crustacea, 
and, as far as is known, to Myriopods. 


Antenne. 


The antenne are the first paired organs to appear. They develop 
from the posterior boundaries of the procephalic lobes, and at Stage 1 
(Plate 1, Figure 1, Plate 2, Figure 8, at.) are stout cylindrical papille 
already faintly constricted into two segments. As Figure 8 shows, they 
are more lateral than the other paired fundaments, and at first far be- 
hind the labrum. Sections prove them to be simple ectodermal evagina- 
tions, like all the other appendieular fundaments. 

At Stages 2 and 3 (Plate 1, Figures 2, 3, at.) the antenne are longer 
and usually composed of three segments. In Figure 2 the fourth seg- 
ment, which normally appears later than Stage 2, is suggested. They 
have now moved forward to positions near the labrum; in Stage 4 
(Plate 1, Figure 4; Plate 3, Figure 12, at.) they lie on the two sides 
of that appendage, and in Stage 5 (Plate 1, Figure 5; Plate 3, Figure 
21, at.) they have attained a position farther forward than the upper lip. 


a ee ee 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. oF 


In Stage 6 (Plate 1, Figure 6, at.) there is clearly indicated a fourth 
antennal segment, which in Stage 7 (Plate 2, Figure 7; Plate 4, Figure 
24, at.) becomes more distinct. At this time the antenne are long and 
stout, and occupy a position still farther forward than before. 

At hatching (Plate 6, Figure 41) they are pre-oral, more slender, dis- 
tinctly segmented, and clothed with sete. 

Elongation of the antenne occurs throughout their entire length, 
judging from the number of cells in longitudinal alignment on the same 
segment at different stages of growth, and also from the frequency of 
karyokinesis in different parts of the appendage. Growth is more rapid, 
however, in the apical region, from which the segments are successively 
constricted. In all the oral fundameuts, in fact, growth was inferred to 
be most rapid at the apex, although likewise occurring throughout the 
rest of the ectodermal layer. At the apex itself— and these remarks 
upply equally well to the legs—the hypodermal cells are larger and 
more turgid than elsewhere, projecting as minute lobes from the surface. 
The chromosomes are very small, but frequently so arranged as strongly 
to suggest mitotic division. 

At Stage 5 (Plate 4, Figure 28, dew’ceb.) an antennary ganglion sup- 
plying the antennal nerves, becomes evident, but finally fuses with the 
first and third ganglia, between which it lies, to form the supracesophageal 
ganglionic mass. 

In Thysanura the antennz develop essentially as I have described for 
Collembola, being likewise at first post-oral and subsequently pre-oral, as 
Uzel (98) has shown for Campodea and Heymons (’97*) for Lepisma. 
Such a migration of the antennz is, however, not peculiar to Aptery- 
gota, but is characteristic of all insects. 

Among Diplopoda but a single pair of antennal fundaments occurs 
(Heymons, ’97°, p. 7, Figur 2, Glomeris). Judging from their position 
in relation to the mouth, they are equivalent to the antennz of Chilo- 
poda, among which Heymons (’97°, p. 4, Figur 1, Scolopendra) has 
discovered two pairs of antennal fundaments. The pre-antennal rudi- 
ments in Chilopoda appear to represent the antenne of insects and the 
antennules of Crustacea, the second pair to be equivalent to the inter- 
calary appendages of insects and the antenne of Diplopods and of 
Crustacea. 

It can scarcely be doubted, in view of the researches of Viallanes (87), 
that the antenne of insects are homologous with the antennules of Crus- 
tacea. In the author’s words (’87, p. 105): “ Voyons maintenant le 
deuxiéme renflement cérébral du Crustacé décapode. II est formé d’une 


98 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


paire de masses nerveuses ventrales connues sous le nom de lobes olfactifs, 
réunies ’une a l’autre par une commissure transverse, et d’une paire de. 
masses dorsales qu’on pourrait désigner sous le nom de lobes dorsaux. 

“Les lobes olfactifs ont une structure tout a fait spéciale; la sub- 
stance ponctuée qui entre dans leur constitution est, pour ainsi dire, 
‘segmentée * en un grand nombre de petites boules d’aspect absolument 
caractéristique, qu’on désigne sous le nom de glomérules olfactifs. Les 
lobes dorsaux, au contraire, n’ont dans leur structure rien qui soit 
spécifique. 

“Le nerf antennaire nait du deuxiéme renflement cérébral par deux 
racines, — lune sort du lobe olfactif, autre du lobe dorsal ; ce dernier, en 
outre, donne naissance a un nerf tégumentaire. 

“Cette description du deuxiéme segment cérébral du Crustacé peut, 
et sans qu il y ait aucun changement a y faire, s’appliquer a I’Insecte, 
tant il y a au point de vue de cette région cérébrale similitude entre les 
deux types. Nous sommes donc en droit d’exprimer cette similitude, en 
appelant du méme nom de deutocérébron le deuxieme segment cérébral, 
qwil s’agisse @’un Crustacé on dun Insecte.” 

In favor of contrary views little can be said. ‘‘ Arguments drawn 
from the absence or presence of either pair of antenne in the higher 
Crustacea are not convincing, as there is great variation in the degree 
of development of their appendages in different groups” (Claypole, ’9g, 
pp. 265-266). Thus, in some Amphipods, the antennules are short, 
and in certain Isopods, extremely reduced. On the other hand, as 
Claypole notes, it is suggestive that in the generalized genus Apus, the 
first antennz are constant and the second variable or absent. 

The fact that the antennules of decapod Crustacea cannot be called 
“ yost-oral”” in origin, is not as significant as it may appear to be. 
The antennules originate at the side of the labrum (Reichenbach, ’g6), 
nearly post-orally, and migrate forward. In view of all other fun- 
damental correspondences between hexapod antennz and crustacean 
antennules, the trifling difference in original position may be ignored, 
especially as the organs in question are eminently migratory. 

I believe, therefore, that the deutocerebrum of Apterygota, repre- 
senting the second somite, is homologous with that of Orthoptera and 
other insects. 


Premandibular Appendages. 
The little-known “premandibular”’ or “intercalary”” appendages are 


important as bearing upon the larger and much-disputed question of 
the segmentation of the head. 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 99 


In Anurida, they are visible in Stages 1 and 2 only, as slight thick- 
enings of the germ band, which are often ill defined in outline and 
hardly deserve the name of appendages. In fact, their demonstration 
is largely a matter of technique. I dissected over thirty germ bands 
for this purpose, stained them variously, and mounted them temporarily 
in weak glycerine, without finding more than suggestions of the inter- 
calary appendages. At this point, Miss Claypole most kindly sent me 
some preparations which were a little clearer than any I had made. 
These I imitated by staining with Delafield’s hematoxylin, decolorizing 
with acid alcohol and mounting without pressure in xylol balsam. If 
care is taken in decolorizing, a condition may be obtained in which all 
of the germ band between the antenne and mandibles has lost color 
excepting a rather vague patch on either side, usually not as distinct as 
in Plate 2, Figure 8°, app. pr’md. ‘These patches are so slightly, if at 
all, elevated that they are not distinguishable with certainty in transverse 
or sagittal sections of the germ band. In good preparations, the lateral 
boundary of either appendage is indicated by a curving row of ectoder- 
mal nuclei, and this resemblance to the other paired fundaments is 
further shown in the presence of an imperfectly developed core of meso- 
dermal nuclei (Figure 8*, ms’drm.). 

Wheeler and Claypole have represented the appendages much smaller 
than I have, and appear to have figured the mesodermal core only. In 
none of Miss Claypole’s slides are the appendages outlined as sharply as 
in the preparation from which my Figure 8* was made. In glycerine 
the yolk granules interfere with proper observation, but in balsam this 
disadvantage is removed. 

Although the appendages are extremely rudimentary, the evidence 
they furnish of the presence of an intercalary segment is reinforced by 
the condition of the nervous system, for there is at Stage 5 a small 
neuromere (Plate 4, Figure 28, érv’ceb.), which, from its relation to the 
remaining cephalic neuromeres, must be regarded as belonging to the 
premandibular segment. It ultimately fuses with the deutocerebrum to 
form a part of the supracesophageal ganglion. 

Viallanes first called attention to the tritocerebral segment of insects 
and Crustacea ; he was afterwards supported by Wheeler, who found 
that it bore a pair of appendages in Anurida; thus Wheeler (’93, p. 57, 
Figure VI.) discovered the intercalary appendages in this species, and 
indicated their obscurity by representing them by broken circles. 
Claypole (98, p. 263, Plate XXIII., Figures 40, 47) also observed 
the appendages, but erroneously inferred that they became modified 


100 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


to form the sides of the face,—a view which I shall discuss 
presently. 

A somewhat similar pair of appendages in the embryo of Apis was 
long ago observed by Biitschli (70), and a few years later by Grassi 
(85) also; but Packard (’98, p. 52, Figure 35) questions whether these 
belong to the category of segmental appendages. 

Heymons (95°, Taf. I., Figur 5) also has recognized the “ Vorkie- 
fersegment ”’ in Orthoptera. He says (’95*, p. 16): “ Letzteres [ Vor- 
kiefersegment] kommt, wie schon gesagt, ttberhaupt nur in ganz 
rudimentirer Weise zur Anlage. Extremitaéten treten an ihm nicht 
mehr auf. Sein Ganglion riickt nach vorn und geht in die Formation 
des Gehirns ein. Bei dieser Gelegenheit werden zugleich auch die éius- 
serlich wahrnehmbaren Spuren des Vorkiefersegments verwischt. Selbst 
im Innen liegen die Verhaltnisse nicht viel giinstiger. Das Mesoderm 
des Vorkiefersegments bildet nimlich bei den Orthopteren ein eigenar- 
tiges Organ, den sogennantes Suboesophagealkorper, welches ebenfalls 
nur eine provisorische Bedeutung besitzt und spiter zu Grunde geht.” 

The same author (’97°, p. 590, Figur II.; Taf. XXX., Figuren 17, 
20), referring to the embryo of Lepisma, writes (p. 591), “‘Genau auf 
der Grenze zwischen dem verbreiterten vorderen Kopfabschnitt und dem 
darauf folgenden verjiingten Korpertheil zeigen sich ferner zwei, aller- 
dings nur schwach markirte, laterale Vordickungen (77c.). Dieselben 
kennzeichnen die Region des rudimentiren Vorkiefer- (Intercalar) Seg- 
mentes. An diesen Segmente kommen wahrend der Entwicklung von 
Lepisma Extremititen nicht zur Ausbildung.” This nearly agrees with 
the condition in Anurida. 

Uzel records distinct intercalary appendages for Campodea in his pre- 
liminary paper (97°, p. 232), and in his final work (98, p. 26) says: 
“Sehen wir auf dem sogenannten Intercalarsegmente (Vorkieferseg- 
mente), das sehr deutlich entwickelt ist, jederseits eine kleine Erhohung 
auftreten (int.), welche als die Extremitiaitenanlagen dieses Segmentes 
zu deuten sind.” (p. 37.) ‘ Die Extremitaten dieses Segmentes werden 
bei Campodea in Form zweier Hocker angelegt, welche sich, wie wir 
voraussenden wollen, bis in das geschlechtereife Alter erhalten, und hier 
als Bestandtheile der ausgebildeten Mundwerkzeuge fungieren (der 
einzige bekannte Fall unter dem Insecten), indem aus ihnen kleine, 
praeoral gelegene, beiderseits an der Wurzel der Oberlippe befindliche 
Lappen (die Intercalarlappen, Taf. VI., Fig. 85, cnt.) entstehen. Bei 
Lepisma sind keine Extremitiétenanlagen auf dem Intercalarsegmente 
vorhanden.” . . . “ Unter den Myriopoden wurden von Zograf bei 


_ 


I eee 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 101 


den Embryonen von Geophilus ziemlich weit hinter dem Munde und 
dicht vor den Anlagen der Mandibelnu zwei ansehnliche Hocker be- 
schrieben und abgebildet, welche wahrscheinlich den Héckern auf dem 
Intercalarsegmente von Campodea homolog sind. Sie werden nach dem 
erwihnten Autor immer kleiner und kleiner und sollen endlich ganz 
verschwinden.” 

In Anurida the intercalary thickenings become involved in the folds 
which form the sides of the face, as I shall describe, but I believe they 
are not, as Miss Claypole held, the fundaments of those folds. 

In Tomocerus and Orchesella (Folsom, ’99, p. 14, Plate 2, Figure 9) 
I have found that “at either end of the [labral] hinge... the cuticula 
is swollen into a conspicuous chitinous lobe, which projects into the 
pharynx to fit against a corresponding prominence of the mandible,” ete. 
As these lobes in the adult occupy precisely the same positions as those 
of Campodea (Uzel, ’98, Taf. VI., Figur 85, int.), I believe them to be 
intercalary appendages. In Anurida no such lobes exist. 

In Chilopods, two pairs of antennal fundaments appear (Heymons, '97°, 
p- 4, Figur 1, Scolopendra), and the second, which alone become func- 
tional, are equivalent in position to the intercalary appendages of 
Apterygota as well as the antenne of Diplopods (cf. Heymons, 97°, p. 7, 
Figur 2, Glomeris). 

The equivalence of the tritocerebrum in Hexapoda and Crustacea was 
first shown in detail by Viallanes. His account (’87, pp. 105-108) is 
too long to be quoted in full, but he concludes: “Les deux lobes con- 
stitutifs du tritocérébron de l’Insecte, et que j’ai désignés sous le nom 
de lobes tritocérébraux, représentent exactement les deux ganglions 
cesophagiens du Crustacé; ils donnent naissance aux mémes racines 
nerveuses, ils sont, comme ces derniers, unis au-dessous de lcesophage 
par la commissure transverse de l’anneau cesophagien.” 

Many authors (Korschelt und Heider, ’90-93, p. 906) agree in homolo- 
gizing the antennz of Hexapoda, innervated from the deutocerebrum, 
with the first antennz of Crustacea ; also in homologizing the mandibles 
of both groups. Therefore only the intervening appendages of the trito- 
cerebrum remain to represent the second antenne of Crustacea. 

An intercalary segment, then, is to be recognized among Pterygota, 
at least in the more generalized forms, and especially among the primi- 
tive Apterygota, and in the latter group it may bear rudimentary appen- 
dages, even in the adult. The intercalary segment is to be regarded as 
equivalent in morphological value to any primary head-segment, —es- 
pecially because it bears a primitive ganglion, — and it constitutes the 

VOL. XXXVI. — NO. 6 2 


102 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


third head somite. The tritocerebrum of Hexapoda is equivalent to 
that of decapod Crustacea, and the intercalary appendages of the former 
are homologous with the second antennz of the latter, and probably 
with the antenne of Chilopoda and Diplopoda. 


Mandibles. 


The fundaments of the mandibles appear in Stage 1 (Plate 1, Figure 
1, md.; Plate 2, Figure 8) as a pair of sub-hemispherical papille be- 
hind the antennz, and considerably nearer than they to the median 
plane. At Stage 2 (Plate 1, Figure 2, md.) they are longer and bluntly 
conical ; but at Stage 3 (Plate 1, Figure 3; Plate 2, Figure 9, md.) in 
lateral aspect they appear shorter than before, because the base is coy- 
ered by a lateral fold of the germ band (Figure 9, pli.or.). Sections 
through the mandibles transverse to the germ band (Plate 3, Figure 16) 
show that they are low broad ectodermal evaginations containing meso- 
derm. In Stage 4 (Plate 1, Figure 4; Plate 3, Figure 19, md.) the 
mandibles, although they have become long and cylindrical, are largely 
covered by the lateral folds ( pl. or.) which have grown more rapidly 
than they ; and in the following stage (Plate 1, Figure 5; Plate 3, Fig- 
ure 20, md.), though still nearly perpendicular to the germ band, they 
are almost completely covered laterally by the folds. The mutual rela- 
tions of mandibles and folds are shown in transections of the germ 
band (Plate 4, Figure 23), in which it may also be seen that the man- 
dibles (md.) are swollen at their ends, their lateral surfaces conforming 
to the adjacent surfaces of the folds (plz. or.). The long axes of the 
mandibles converge at their bases toward the median plane, and it is 
noteworthy that the lateral surface of each mandible is distinctly longer 
than the mesal surface (Figure 23, md.)—a foreshadowing of the 
oblique orifice of the finished organ. 

At Stage 7 (Plate 2, Figure 7; Plate 4, Figure 24, md.) the mandibles, 
now wholly covered by the lateral folds (plz. or.), are much longer and 
still conical ; they are shorter and much more slender than the under- 
lying first maxillee ;-and instead of being perpendicular to the germ 
band, they have now swung forward through an angle of almost ninety 
degrees ; moreover, they converge in front toward the median plane, as 
do the first maxille (Plate 5, Figure 29). In this stage the mandibular 
muscles are individually distinguishable (Figure 32), and the anterior 
extremity of the mandible bears several minute lobes (Figure 32), each 
consisting of a single hypodermal cell. Inthe next (8th) stage the free 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 103 


end continues to bend toward the median plane until the apices of both 
mandibles meet. The terminal unicellular lobes become multicellular and 
secrete the incisive teeth (Plate 6, Figure 37 de. 7’cvs.), of which there are 
finally five principal ones on the right and six on the left mandible. 
Althongh the “head” of the completed organ is almost solid chitin 
(Plate 6, Figure 37), there are five canals, one penetrating the base of 
each tooth ; the hypodermal cells have, however, receded from the 
“ head.” 

The extreme basal end of the finished mandible is prolonged as a 
chitinous, conical projection (Plate 6, Figure 36, cdz.), which, as in 
Orchesella, is let into a concave chitinous piece that I have called the 
stirrup (sta.), from which it may be withdrawn when the mandibles are 
protruded. This projection, or pivot, arises in Stage 7 (Plate 5, Figure 
32, edz.) as a hypodermal evagiuation of the mandibular fundament, and 
simultaneously the chitinous stirrup (sta.) is formed in a transverse, 
superficial groove of the hypodermis lining the pharyngeal pocket in 
which the mandible lies. In Orchesella the lateral end of the stirrup 
unites with the external cuticula of the skull after traversing two layers 
of hypodermis: first, the layer lining the mandibular pocket, and 
second, the superficial layer of the head ; in Anurida, however, I have 
found no such union between stirrup and skull. The body of the man- 
dible is simply a modified cone, and hence in sections across this region 
appears as a complete chitinous ring (Plate 7, Figures 44, 45, md.). 

In Anurida no trace of a mandibular palpus exists at any stage, and, 
unlike Orchesella, no molar surface is differentiated ; the latter fact is 
correlated with the character of the food: Orchesella feeds upon ligni- 
fied vegetable substances, Anurida upon the soft tissues of the mollusk 
Littorina littoria. In further correlation with diet, the powerful rota- 
tors, or grinding muscles, of Orchesella are not represented in Anurida. 

Several writers on Collembola have already given surface views of the 
mandibular fundaments at early stages, although none have traced their 
development. I refer especially to Lemoine (’83, Smynthurus) and 
Wheeler (93, p. 57, Figure VI., Anurida). Packard (’71, p. 17; 
Plate 3, Figure 13) evidently overlooked the mandibular fundaments of 
Isotoma, and what he regarded as mandibles are clearly, from their 
position, the first maxilla. Ryder (’86) made the same mistake. 

Claypole (’98, Plate XXIII.) gives several figures of the mandibular 
fundaments of Anurida maritima before much differentiation has oc- 
curred, and Uzel (’98, Taf. VI., Figur 87) represents the fundaments 
in Macrotoma (Tomocerus) at a stage equivalent to that of my Figure 


104 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


21. He also gives a figure (Taf. V., Figur 64) supporting his state- 
ment (p. 22) concerning the appearance of the mandibular segments: 
“ Ausserdem [collection of entoderm cells, etc. ] bemerkt man zwei Paar 
dunkler Stelle, welche an den Ecken eines gedachten Quadrats sich 
befinden. Das dem Dorsalorgane geniherte Paar dieser Blastodermver- 
dickungen (4/.) sind die getrennten Anlagen der Kopflappen, das zweite 
Paar (mds.) stellt die getrennten Anlagen des Mandibularsegmentes vor.” 
The eggs of Anurida at my disposal were either too old or too young to 
show the condition here described by Uzel, although I did find a stage 
in which three pairs of fundaments were present, the third pair being 
the first maxilla. The mandibles probably follow the procephalic lobes 
in appearance, as I have found all the stages necessary to indicate that 
the remaining paired appendages, except those of the superlingue, as I 
shall term them, appear successively from in front backward. 

Campodea is structurally nearest to the Collembola, and, thanks to 
Uzel (98, Taf. IIL, Figuren 35, 36; Taf. VI., Figuren 77-85), some- 
thing is known concerning the development of its mouth-parts. The 
mandibular fundaments of Campodea are simple papille, as in Collem- 
bola ; this simplicity distinguishes the Apterygota from the most gener- 
alized Pterygota, the Orthoptera, in which the fundaments are sometimes 
lobed. 

The finished mandible of Campodea is strikingly like that of the 
Collembola, and is, moreover, of great morphological interest, because 
the structural correspondence of the mandible with the maxilla of hexa- 
pods — obscure in almost all other insects —is here a matter of direct 
observation, not merely one of inference. The mandible of Campodea 
(Meinert, ’65, Taf. XIV., Figuren 15, 16; Nassonow, ’87, p. 33, Figur 
27) consists of a hollow fulerum (stipes) and a head, which is separated 
from the fulcrum by a transverse suture. The head is composed of two 
parts, — a large, toothed, immovable, outer lobe or galea, and a smaller, 
fringed, movable, inner lobe, representing the lacinia. 

Accepting the homologies with the first maxillee implied in these 
terms, the palpus remains to be accounted for. A mandibular palpus has 
never been found among adult insects, — the evidence given for one 
by Hollis (’72) being quite vague and inadequate. Although the de- 
tailed development of the mouth-parts of Campodea has never been 
followed, it is in this most generalized insect that one may most hope- 
fully look for a trace of a mandibular palpus, and we may safely predict 
that, if found, it will be a lateral, distal lobe of the stipal region, just as 
it is in the maxille of all insects. 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 105 


The agreement between the finished mandibles of Campodea and 
Japyx, on the one hand, and Collembola, as represented by Anurida and 
Orchesella, on the other hand, is remarkably close. In both groups the 
mandible is hollow, has an oblique basal opening, which is large in Cam- 
podea, and, instead of an ordinary articulation, a free basal pivot, which 
is peculiar to the Apterygota. The homologies extend further, for I 
find that the similar and complicated movements of the mandibles are 
actually effected by muscles which are probably homologous in the two 
groups. The equivalence of certain muscles in Campodea, as repre- 
sented by Meinert (65, Taf. XIV., Figure 15) with others figured by 
myself for Orchesella (Folsom, ’99, Plate 2, Figures 14, 15) may be ex- 
pressed in tabular form as follows : — 


Campodea (Meinert). Orchesella (Folsom). 
Muscle C’ (distal) corresponds with 9. add. 

«_ C (proximal) ae Sa eforrotil. 

< -D «6 xe 5. prt.t. and 6. prt. ms. 

oe as) D; G se 3. ret. rot. and 4. ret., or else 7. rot. 


and 8. rot. 


The incompleteness of Meinert’s figure prevents as exact a comparison 
as is desirable. 

Japyx is nearest Campodea in structure, and the mandibles of Japyx, 
which have been described and figured by Meinert (65), Grassi (’86°), 
and v. Stummer-Traunfels (91), are essentially like those of Campodea, 
but lack the articulated lacinial lobe, there being a lacinial region, how- 
ever, which (Grassi, ’86°, Taf. II., Figura 14) is separated by a trans- 
verse line from the fulcrum. The muscles of Japyx agree with those of 
Campodea, and it is to be noted that the adductors originate upon a 
median chitinous plate, or tentorium, just as in Collembola, but not as 
in Orthoptera. The muscle f of Meinert (65, Taf. XIV., Figuren 5, 15) 
has no homologue, it should be said, among the mandibular muscles of 
Orchesella, and I should be disposed to regard it as an adductor of the 
head of the first maxilla, had not v. Stummer-Traunfels (91, Taf. I, 
Figuren 1, 3) figured the tendon of the same muscle in Campodea and 
Japyx going to the mandible. This author (91, p. 220) erroneously 
states that the adductors of Collembola, Campodea, and Japyx are at- 
tached to the “ Stiitzapparate,” by which he means the lingual stalks 
(Plate 6, Figure 38, pd.) ; these, however, are quite distinct from the 
tentorium, which he apparently overlooked. 

Nearly allied to the entognathous genera Campodea and Japyx are 
the ectognathous genera Lepisma and Machilis. In Lepisma the early 


106 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


development of the mandibles, as shown by Heymons (’97°%, Taf. XXX., 
Figuren 13; 15, 17, 20), is simple, and agrees with that of Anurida and 
Campodea. The finished mandible of Machilis (Oudemauns, ’88, Plate 
IL., Figuren 25, 26), especially, recalls that of Campodea and Collem- 
bola by its elongated hollow fulcrum, oblique aperture, basal pivot, 
distinct head, and (as in Orchesella) well-developed molar surface ; 
moreover, the adductors originate ona tentorium and are inserted within 
the mandibles (Oudemans, ’88, Taf. 1, Figur 19; Wood-Mason, 779, 
p- 148, Figure 1). Wood-Mason named the apex of the mandible “ ex- 
opodite” and the molar lobe “ endopodite,” but upon superficial grounds, 
if one may judge from the evidence of embryology. Both lobes may 
together represent the endopodite ; but the exopodite, or palpus,.is un- 
represented in the mandible, and it is a secondary lobe of the primary, 
or stipal, fundament, in the first and second maxilla. Wood-Mason 
(79) pointed out many interesting similarities which Machilis and 
Lepisma bear to the most generalized Orthopteran family, the Blattide, 
and remarked (p. 149), concerning the pivot of Machilis, that “the pos- 
terior ball-shaped condyle of mandibulated insects, clearly foreshadowed 
in the myriapod, is here fully formed and provided with a distinet neck.” 

The mandibles of Lepisma, however, more closely approach the Or- 
thopteran type in being compact (v. Stummer-Traunfels, 91, Taf. IT., 
Figuren 5, 6) and partly solidified, and in having broad incisive teeth, 
a molar surface like that of Orthoptera, and broadly attached adductors. 
The muscles are said by Oudemans (’88, p. 187) to resemble those of 
Machilis. V. Stummer-Traunfels represents the adductors only, and it 
may well be that the muscles are really much fewer than in Campodea | 
and Collembola, such a reduction in number, if it occurs, being an 
approach to the Orthopteran type, in which but two mandibular muscles 
exist — a stout adductor and a slender abductor. 

As to the development of the mandibles in Orthoptera, very little has 
been published. Ayers (’84, p. 241, Plate 18, Figures 20-22) says that 
in @icanthus “the three oral appendages are trilobed ; the lobation is 
most prominent in the second maxillary and least in the mandibular 
appendage. The primitive appendage is first divided into two lobes, 
and the inner of these becomes secondarily divided into two.’ The 
three lobes doubtless represent palpus, galea, and lacinia. Korotneff 
(85, Taf. XXIX., Figure 6) figures lobed mandibular fundaments for 
aryllotalpa, In other Orthoptera such lobation has not been recorded. 
In Blatta, according to Wheeler (’89, p. 348), “There are apparently 
no traces of lobation in the mandibles.” Packard (’83*, p. 279) says, 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 107 


“ The mandibles [of Caloptenus] remain single-lobed,” and both Wheeler 
(’93) and Heymons (’95") represent them as simple papille in all fami- 
lies of Orthoptera. It may at least be said, however, that the mandibles 
of Collembola and Thysanura are certainly homologous in their entirety 
with those of Orthoptera, and hence of all other insects. 

It is an interesting fact that Heymons (96, Taf. II., Figur 29) dis- 
tinctly represents mandibular palpi for the larva of Ephemera, 
condition ; indeed, Packard (’98, p. 61) terms this appendage of nymphal 
Ephemerids a “lacinia-like” process, although Heymons states (p. 21) 
that it is lateral in position, and so figures it. 

What embryological evidence there is, then, confirms the view based 
upon anatomical data, that “the mandibles are primarily three-lobed 
appendages like the maxillz ” (Packard, ’98, p. 61). 

Turning now to the Myriopoda, the Symphyla, represented by the 
single genus Scolopendrella, show marked affinities with Campodea, as 
is well known. I wish here to emphasize especially the correspondences 


a rare 


between the mouth-parts of the two genera, which have never been 
carefully compared in these respects. 

Latzel (’84, p. 8, Taf. I., Figur 5) describes the mandibles of Scolo- 
pendrella as follows : ‘‘ Die Oberkiefer bestehen jederseits aus einer fast 
horizontal gelagerten, trapezoidalen Chitinplatte, welche am End- oder 
Kaurande durch eine mittlere Einbuchtung in zwei Partien abgetheilt 
erscheint, von denen die vordere in vier kriftige, die hintere in vier bis 
fiinf kleinere Zailnchen eingeschnitten ist. Eingelenkt sind diese Kie- 
ferplatten mit dem hinteren und dusseren Eck in eine zwischen Kopf- 
decke und Unterseite eingelagerte seitliche Lamina, welche einige 
Aehnlichkeit hat mit der Wange der Insecten und die von Menge als 
Theil (Stamm) der Oberkiefer aufgefasst wird. Am inneren Hintereck 
jeder der beiden Oberkieferplatten entspringt eine sehr kriaftige Sehne, 
die in eine betrachtliche Anzahl von Muskelbiindeln auslauft, welche sich 
unten am Kopfrahmen inseriren.” 

The mandibles of Scolopendrella therefore resemble those of Cam- 
podea rather than those of any other insect, in that they are hollow, 
with a basal (stipal) part articulated to the skull, and a head separated 
transversely from the fulcrum. The head consists of two primary lobes 
(galea and lacinia) as in Campodea, but both are movable by muscles, 
whereas in Campodea the lacinia alone is articulated, and even this no 
longer has muscular attachments. Thetendon and muscles which move 
the lacinia of Scolopendrella are exactly similar in position and function 
to the “chitinous rod” and muscles which adduct the head of the first 


108 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


maxilla of Orchesella, Japyx (Meinert, ’65, Taf. XIV., Figur 8) and 
doubtless Campodea. More important, however, is the fact that the 
tendon of Scolopendrella is comparable with the mandibular retractor 
(cf. Latzel, 84, Taf. 1, Figur 5, «, and Meinert, ’65, Taf. XIV., Figuren 
5, 15, f,, flecor) of Campodea and Japyx, and may be homologous with it. 
It can be easily understood that, if the terminal lobes in Scolopendrella 
became immovable by solidification in the mandible, the adductors of 
those lobes would then serve as retractors of the entire mandible, as in 
Campodea and Japyx. 

Grassi (’86*, pp. 15-16, Tav. II., Figure 2, 5) supplements Latzel’s 
account of Scolopendrella by saying that no true cardo is present, and 
that the mandible is capable of lateral movements only. 

Packard (83°, p. 198) says, “The so-called mandibles of the Myrio- 
pods are the morphological equivalents of those of insects, but structur- 
ally they are not homologous with them, but rather resemble the lacinia 
of the hexapodous maxilla.’ With the last assertion I do not agree. 
The mandibles of the more generalized Diplopods are in detail strikingly 
like those of Scolopendrella (Latzel, ’g4, Taf. I, Figur 5); for example, 
those of Polyzonium (Latzel, ’84, Taf. XVI., Figur 203), in which the 
only fundamental difference is the presence of a cardo in Polyzonium, the 
stipes, galea, lacinia, and tendon being essentially as in Scolopendrella. 
The mandible, or protomala (Metschnikoff, 75), of Polyzonium does, in- 
deed, resemble, not the lacinia, but the entire first maxilla of Thysanura 
and Collembola. The similarity, however, should not be mistaken for 
homology ; it rather serves to emphasize the structural agreement of 
mandibles and maxille,—an agreement which gradually becomes ob- 
scure in the insect series through the progressive solidification of the 
mandible, but may nevertheless be traced, as I have shown, from Diplo- 
podaand Symphyla, through Campodea and Japyx, Machilis and Lepisma, 
to the more generalized Orthoptera ; thus the differences between the 
mandibles of Diplopods and Insects are not so great as Packard has 
affirmed (’98, p. 12). 

The most that is known about the development of Diplopod mouth- 
parts we owe to Metschnikoff (’74), who represents only two pairs of 
oral fundaments, designated ‘‘ mandibles ” and “labium.” Although this 
conclusion is also reached by vom Rath (’86), I would not infer with 
Packard (’83°, p. 199) that there can be only two pairs of oral appen- 
dages, but would suggest that embryological studies upon the mouth- 
parts of other Diplopoda may, perhaps, show more. 

The mandibles, or protomale, of Chilopoda are generally recognized as 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 109 


equivalent to those of Chilognatha, and, indeed, to the mandibles of Hexa- 
poda and Crustacea. In the mandibles of Scolopendra (Meinert, ’83, 
Taf. II., Figur 9), for example, there can be recognized cardo and stipes, 
a distinct head with galeal and lacinial lobes, and even muscles exactly 
comparable with the adductors and retractors of the mandible in Campodea 
and Japyx. ‘The affinities of the Chilopods are, however, with the Dip- 
lopods, — from the stem-form of which they may have developed, — 
rather than with the Campodeide. Although Packard (98, p. 15) 
states, “In the Chilopoda also the parts of the head, except the epi- 
cranium, are not homologous with those of insects, neither are the 
mouth-parts,”’ there is really much indirect evidence of homology 
with the mouth-parts of insects through Diplopoda, Symphyla, and 
Thysanura, as is indicated above. 

The mandibles of Crustacea have usually been considered homologous 
with those of insects. In Malacostraca (Reichenbach, ’86), as in in- 
sects, the mandibular fundaments are a pair of appendages of the fourth 
primitive segment. In insects the exopodite (palpus) is absent, but in 
such generalized groups as Campodea and certain Ephemeride, a “ Jacinia 
mobilis” is present ; in Malacostraca the palpus is present, and like- 
wise, according to Hansen, a similar lacinia is found in the groups 
Mysida, Cumacea, Isopoda, and Amphipoda, although not in Decapoda. 

Among insects, the Thysanura most nearly approach Crustacea. 
Hansen (93, pp. 205-206) says of Machilis: ‘Die Mandibeln sind 
homolog mit denen der Malacostraken ; in Form sind sie denen der 
Cumaceen ahnlich, mit einer gut entwickelten, fast cylindrischen Pars 
molaris, doch ohne Lacinia mobilis; in Einlenkung und Musculatur 
stimmen sie erstaunend iiberein mit z. B. Diastylis und Nebalia.” Re- 
ferring to Campodea, Japyx, and Collembola, he remarks (pp. 208-209), 
‘Die Musculatur der Mandibeln ist noch mehr der Crustaceen iihnlich 
als der Musculatur der Machilis. Vergleiche Meinert’s Figur von 
Japyx mit meiner Figur von Diastylis Goodsiri in ‘ Dijmphna-Togtet’ 
(ich habe nur die drei gréssten Muskeln oder ihre Sehnen wiedergege- 
ben) oder mit Sars’ Figur von Diastylis sculpta, und man wird betroffen 
von der erstaunlichen Uebereinstimmung in Form und Richtung der 
Muskeln und der grossen medianen Muskelplatte.”’ 

In conclusion, the mandibles of Apterygota agree in development with 
those of Orthoptera, but show no trace of lobation except in Campodea, 
the most primitive form. The mandibles and maxillze are homodyna- 
mous, and the former are homologous with the mandibles of Scolopen- 
drella, Crustacea, and probably Diplopoda. 


110 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 


Lingua and Superlingue. 


Not until Stage 3 are the fundaments of the superlingue (“ para- 
gloss ” of some authors) observed ; then a ventral aspect of the germ 
band (Plate 3, Figure 11) reveals two small papille (sw’/ng.) between 
the mandibles with their centres slightly more anterior than those of 
the mandibles. Although each small papilla is adjacent or contiguous 
to the mandibular fundament of the same side, it originates quite inde- 
pendently ; in other words, it is not the inner branch of a biramous ap- 
pendage, but a distinct ectodermal evagination, as transections of the 
germ band (Plate 4, Figure 23, sw’Ing.) prove. 

At Stage 4 (Plate 3, Fig. 12, sw’lng.) the superlingual fundaments 
are longer and stouter than before, and have moved back slightly in re- 
lation to the mandibles.until nearly opposite them. 

At Stage 5 the centres of the superlinguz (Plate 3, Figure 21, sw’ Ing.) 
are behind those of the mandibles, and in cross-sections (Plate 4, Figure 
23) the former structures are seen to have exceeded the latter in rate 
of elongation. The long axes of the superlingue now diverge anteriorly 
from the median plane and the apices are partly under the mandibles, 
as in the adult, though the bases retain nearly their original positions in 
relation to the bases of the mandibles. During this stage is seen the 
first trace of the lingua (the “ligula,” or “hypopharynx” of some 
authors), as a slight, median, unpaired, oval, ectodermal evagination 
(Plate 3, Figure 21, dng.) between the first maxilla. This is the last of 
the oral fundaments to make its appearance. 

In Stages 6 and 7 the lingua becomes longer and stouter, and, as 
seen in a ventral view of the germ band (Plate 5, Figure 30, Ing.), its 
cross-section is rounded-triangular with its anterior median angle intrud- 
ing between the two superlinguze. Sections show that the lingua and 
superlingue have swung forward from their former positions at right 
angles to the germ band, and that the lingual and superlingual cavities 
are separately confluent with the general body cavity of the head. In 
the region of confluence a common cavity —a prolongation of the body 
cavity —is formed by a median evagination of the germ band itself. 
In Apterygota the superlinguz, however, never become appendages of 
the lingua. 

In ventral aspect, the lingua at Stage 7 (Plate 4, Figure 27 ; Plate 5, 
Figure 29) is cuneate with rounded apex, and, a little later (Plate 4, 
Figure 25, Ing.) becomes constricted distally, forming a terminal Jobe. 

In Stage 8 the lateral surfaces (Plate 5, Figure 34) become concave, 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 195i: 


to correspond with the adjacent convex surfaces of the first maxille, as 
in the adult (Plate 7, Figures 44, 45, ehé.), and each ventro-lateral edge 
extends under the neighboring maxilla; in addition, the apex of the 
lingua becomes separated into two lateral lobes by a median sinus, and 
the dorsal surface invaginates to form a median longitudinal groove 
(Plate 7, Figure 42, sud.) ; this lobed condition, however, is quite 
secondary in origin. 

The lingua is thickly chitinized, and the hypodermal cells persist in 
the mature organ. The superlinguz, on the contrary, are but thinly 
chitinized and at maturity contain no distinct hypodermis cells, except 
basally, although a complete layer of cells exists in Stage 8. In this 
stage (8) the superlinguz become triangular in cross-section, as in the 
adult (Plate 7, Figure 44). Partly on account of the divergence of 
the superlinguz in front, but principally owing to the convergence of 
the mandibles and maxille, the attenuated distal part of each superlingua 
becomes situated between the apices of the mandible and the first 
maxilla of the same side (Figure 44), and the superlinguze conform to 
the adjacent surfaces of the maxille. 

The most interesting lingual structures are the two basal stalks 
(Plate 6, Figure 38, pd.'), each of which articulates with the cardo of 
the same side and also furnishes a firm origin for the adductors and re- 
tractors of the first maxilla, as in Orchesella (Folsom, ’99, Plate 3, Fig- 
ure 21). The development of these stalks has never been described. 
Although difficult to comprehend with a knowledge of the finished con- 
dition only, it is simpler than might be expected. The key to the 
understanding of its origin is the fact that each chitinous stalk is formed 
in a groove which is but a longitudinal evagination of the maxillary 
pocket, and follows the mesal surface of the first maxilla back to the 
cardo. The base of the lingual fundament is at da. in Figure 30 (Plate 
5), and that of the maxilla at ba.!; consequently the stalk is developed 
in a superficial groove of the germ band itself — that part of the germ 
band connecting the base of the lingua with the extreme base of the 
maxilla, In ventral aspect at Stage 7 (Plate 5, Figure 29, pd.’), the 
continuity of the stalk along the surface of the maxillary pocket is evi- 
dent. Dorsal to the stalk, of course, the base of the maxilla is connected 
with the head, but under the connecting region passes the stalk. 

I must now explain how maxillary muscles become attached to the 
stalk in spite of the fact that the latter is a superficial formation of the 
hypodermis. This may be learned from transections at Stages 7 and 8, 
but also, and more easily, from good serial sections of an adult head, 


112 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


such as are shown in Plate 7, Figures 46-50, which successively repre- 
sent sections in more posterior planes. 

Figure 46 shows the right maxilla (mz.") sectioned in front of its basal 
opening and lying free in its pharyngeal pocket ; it also shows the stout, 
superficial chitinous stalk (pd.’) in its hypodermal groove. Figure 47 
represents the beginning of an evagination (plz.) of the dorsal wall of 
the pocket, which grows down between the maxilla and chitinous stalk. 
Passing back, the intruding hypodermal fold expands, as in Figures 48 
and 49 (plv.), until it almost encloses the stalk. Finally, in the region 
of the maxillary aperture (Figure 50), and on account of its obliquity, 
adductor muscles (mw.) are enabled to pass directly from the inner wall 
of the stipes to the chitinous stalk (pd.’). They are not attached di- 
rectly to the stalk, but to an intervening cuticula (cta.) ; this, however, 
amounts to the same thing, because the cuticula and stalk become fused 
together at about Stage 7, and hardened into a single piece. It should 
be stated that the hypodermal cells which formed the intervening 
cuticula, as well as those which formed the stipes, are seen in em- 
bryological life only; they disappear at the origin and insertion of 
muscles. 

At Stage 7 the end of each stalk is already feebly fused with the end 
of the cardo to form an articulation (compare Plate 4, Figure 25, with 
Plate 6, Figure 38, atc.). This is a simple process, as both cardo and 
stipes are superficial and contiguous structures. In the adult Orchesella 
(Folsom, ’99, Plate 2, Figure 10, /¢g.') a long ligament unites them, and 
I mentioned a distinct suture as possibly indicating the end-to-end union 
of two ligaments, which doubtless occurred. 

The lingual stalks, then, are quite independent of the lingua in origin, 
except that they are thickened cuticular structures continuous with the 
lateral cuticula (Plate 7, Figure 45, cht.) of the lingua. When dissect- 
ing out the lingua at Stage 7, it frequently breaks away from the stalks 
at the sutures (swt.) shown in Plate 4, Figure 25 ; these sutures later 
become obliterated, however. 

The lingual stalks of Collembola have been mentioned by several 
authors, for example, de Olfers (’62, p. 18) in several genera, Tullberg 
(72, Taf. IV., Figur 17) in Tomocerus, and v. Stummer-Traunfels 
(91, Taf. I. Figur 7) in Tetrodontophora. I have seen them myself 
in all the more common genera; they undergo but little modification 
within the order. 

As to the development of the lingua and superlinguz in other insects, 
very little has been written. Packard (’71, p. 17), as quoted on page 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. Ls 


128, did not find the “second maxille” (superlingue) in the embryo 
of Isotoma. Uzel alone has mentioned the embryonic lingua and super- 
linguee of Apterygota. In Taf. VI. Fig. 87, he shows, in Tomocerus, 
three fundaments, which undoubtedly are these structures. 

In Campodea, happily, Uzel describes with some detail the develop- 
ment of the “hypopharynx” (98, p. 35): “Schon in jenem Stadium, 
bei welchem der Keimstreif sich in seinen mittleren Theilen in das 
Innere des Dotters einzusenken anfiangt (Taf. IV. Figur 39), bemerken 
wir zwischen den beiden Anlagen der Mandibeln zwei einander sehr 
geniherte, ziemlich grosse, flache Platten (Amd.). Diese werden im 
nichsten Stadium, in dem die Umrollung des Keimstreifs vollendet ist, 
viel kleiner (Taf. VI. Figur 81, md.) ; dafiir w6lben sie sich jedoch 
bedeutend zu zwei spitzigen Hoéckern vor. Bald erscheint zwischen den 
Anlagen der ersten Maxillen eine unpaare, grosse, flache Platte (Figur 
82, hmx.,), vor der man eine kleinere sieht. Letztere befindet sich zwi- 
schen den beiden vorher beschriebenen spitzigen Héckern und gehort 
noch dem Mandibularsegmente an (Figure 83, hmd.’). Die unpaare, dem 
ersten Maxillarsegmente angehorende Platte schickt sich nun an, tiber 
die beiden Hocker und die zwischen denselben gelegene kleine Platte 
vorzuwachsen (Figur 84), und zwar etwa in der Zeit, zu welcher das Thier 
ausschliipft.” After hatching, continues Uzel (98, p. 48), ‘“ Von den 
drei schon friiher beschriebenen Héckern, die zwischen den beiden 
Anlagen der Mandibeln lagen, wird der mittlere immer kleiner. Bei 
dem erwachsenden Thiere haben sich die beiden seitlichen zu runden 
bewimperten Schuppen ungebildet, welche von Meinert (67) als Para- 
glossee bezeichnet worden sind. Zwischen denselben befindet sich der 
nun sehr klein gewordene mittlere Hocker als unbedeutendes Gebilde, 
welches die beiden seitlichen Schuppen verbindet. Die gréssere, zwi- 
schen den beiden Anlagen der ersten Maxillen gelegene Platte hat sich 
auch in eine, aber entsprechend der miichtigeren Anlage, grossere 
Schuppe verwandelt und ist itber die beiden Schuppen des Mandibular- 
segmentes erst beim geschlechtsreifen Thiere giinzlich vorgewachsen 
(Taf. VI. Figure 85, hmz.,). Sie stellt Meinerts Ligula vor. Sowohl 
die von Meinert (’67) als Paraglossz, als auch die von demselben als 
Ligula gedeuteten Theile sind, wie wir gesehen haben, ihrer Anlage 
nach als Hypopharynx aufzufassen.” 

The “hypopharynx ” of Campodea is, then, undoubtedly homologous 
with the lingua and superlingue of Anurida, with the development of 
which it fundamentally agrees. In Anurida, however, as contrasted 
with Campodea, the superlingual fundaments do not show the early 


114 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


decrease in size, and a small median lobe does not appear on the anterior 
surface of the lingua. 

In the finished condition in Campodea (Meinert, ’65, Taf. XIV. Fig- 
uren 17, 19) lingua and superlingue are simple but distinct lobes, and 
the small fourth lobe mentioned by Uzel persists. The lingual stalks 
are surprisingly like those of Orchesella ; the articulation with the cardo 
Meinert did not show, but it has since been observed by v. Stummer- 
Traunfels. 

The English translator of Meinert’s paper is really responsible for the 
use of the terms “lingua’’ and “paraglosse”’ in connection with this 
subject, and not Meinert himself; the latter writer applied only the 
Danish expressions ‘Tungen” and “ Bitungens tvende Flige.”’ 

Von Stummer-Traunfels (91, Taf. I. Figur 11) also represents the 
“ Ligula,’”’ “ Paraglosse,” and “ Stiitzstiicken ” of Campodea. On page 
121 I criticise this author for holding that the so-called maxillary 
palpus of Collembola belongs to the neighboring superlingua. The em- 
bryology shows that the delicate membrane connecting either palpus 
and superlingna is of quite subsidiary importance, being simply as much 
of the cuticula of the maxillary pocket as intervenes between the base 
of a superlingua and the adjacent maxilla, —in fact, only the anterior 
portion of the cuticula surrounding the tissues which attach the maxilla 
to the head. 

Japyx agrees closely with Campodea in the structure of these organs 
(Meinert, ’65, Taf. XIV. Figur 8 ; von Stummer-Traunfels, ’91, Taf. I. 
Figur 10), and there is no doubt about the homology of the lingua, 
superlingue, and lingual stalks of Japyx with those of Collembola. In 
the words of v. Stummer-Traunfels (’91, p. 221), “ Diese typische Form 
des Stiitzapparates und der Befestigung der Cardines an diesem findet 
sich bei Campodea, Japyx und den Collembola in beinahe identischer 
Weise ausgebildet.” The author is mistaken (91, p. 222), however, in 
saying that the mandibles are attached to the Stiitzapparate, apparently 
having overlooked the tentorium, which is quite another structure than 
his “ Stiitzapparat.” 

Regarding Lepisma, Heymons (’97*, p. 595) simply remarks: “Ich 
. . . bemerke nur, dass die Bildung der einzelnen K6rpertheile, z. B. 
des Hypopharynx der Mundwerkzeuge, durchaus an den bei Orthopteren 
bekannten Typus anschliesst.” 

Machilis, also, has decided Orthopteran affinities, as Wood-Mason (’79) 
found, yet the mouth-parts of both Lepisma and Machilis, although 
ectognathous, as in Orthoptera, are constructed upon fundamentally the 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 115 


same plan as those of the entognathous Apterygota. The similarity is 
evident in part from the following account of Machilis by Oudemans 
(88, p. 186): “ Letztere [Ligula], Figur 28 Zz, reicht mit ihrem freien 
Ende ungefiihr ebensoweit als die Unterlippe und wird durch zwei 
Chitinstibchen gestiitzt, Figur 28 8, Figur 308. Mit der Ligula sind 
noch zwei Stiicke, Figur 30 P, verbunden, die ich als Paraglossz auffassen 
mochte. Sie sitzen an einer Chitinleiste, die sich auf der Dorsalseite der 
Ligula findet. Jede Paraglossa ist an ihrem freien Ende noch einiger- 
massen vertheilt (ich glaube in drei Lobi) und hat einen kleinen Vor- 
sprung an ihrer Basis, Figur 30 A. Es scheint mir, dass die Paraglossze 
ausserdem noch festsitzen an den Stiitzstiickchen der Ligula, Figur 
308.” 

. . » “Die Maxillarspitzen treffen einander mithin in dem Zwischen- 
raum zwischen Ligula und Paragloss, Figur 21, die Mandibularspitzen 
zwischen Paraglossee und Labrum.” 

Von Stummer-Traunfels (91) repeats some of Oudemans’ figures of 
Machilis. 

In Machilis, I find that the first maxille articulate with the skull— 
no longer with the lingual stalks —and the stalks, although evident, 
are much reduced and apparently functionless. The salivary glands 
open, as in Orthoptera, under the base of the lingua. 

In Orthoptera, the most generalized of the Pterygota, there is a well- 
developed hypopharynx, or lingua, which exactly corresponds in position 
with the lingua of Apterygota, being a median papilla between the bases 
of the first and second maxilla. In Periplaneta (Miall and Denny, ’86, 
p- 127, Figure 71) it is borne upon two chitinous stalks, clearly com- 
parable with those in Apterygota. Looking for traces of superlinguze 
in Melanoplus femoratus, I found them, as large dorso-lateral rounded 
lobes, intimately united, however, with the lingua. This union is 
already foreshadowed in Machilis and Lepisma. I also found — almost 
accidentally — two rudimentary, chitinous, divergent stalks, extending 
back into the head from the ventro-lateral regions of the base of the 
lingua. The significance of these facts is clear, although the meaning 
of the lingual appendages, which have apparently been overlooked or 
disregarded in most Orthoptera, could hardly have been ascertained 
without studying the less specialized Apterygota. In Packard’s figure 
of Anabrus (’98, p. 73, Figure 71), also, the lingua and left superlingua 
are evident. 

In the rare and singular Hemimerus, Hansen (94, pp. 70-71, Plate 2, 
Figures 9, 10, h.) finds a “ hypopharynx”’ and “ maxillulz,” as well as 


116 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


chitinous stalks, all of which distinctly are as in Collembola, Campodea, 
and Japyx, except that the superlingue of Hemimerus appear to be 
fused with the lingua. Figure 10 of Hansen bears a close resemblance 
to my Figure 27 of Auurida, although Hansen says (p. 87), “ especially 
the structure of the mouth removes it [Hemimerus] very far [?] from 
the Thysanura and leads it to the Orthoptera.” 

In the young larva of Ephemera, Heymons (’96, p. 22, Taf. II. 
Figur 29) finds that “Der Hypopharynx entsteht . . . auf ahnliche 
Weise wie bei den Orthopteren. Auch an ihm findet eine Art Gliede- 
rung statt, dergestalt, dass von der eigentlichen Hauptmasse zwei laterale 
vordere Zapfen abgetrennt werden, die mit kleinen Harchen bedeckt 
sind, wihrend der eigentliche Hypopharynx am Ende einen Besatz von 
feinen (Sinnes-) Borsten tragt.” His figure of lingua and superlingue 
might fairly represent those structures of Anurida in Stage 7 (Plate 4, 
Figure 27). Inthe imago the mouth-parts are, of course, atrophied. 
In another Ephemerid nymph, Heptagenia, Vayssiére (’82, pp. 113- 
114, Planche 5, Figure 46) found a highly developed lingua, or hypo- 
pharynx, fused with large lateral pieces [superlingue ] and suggests that 
they indicate a distinct primitive segment, —a possibility which will be 
discussed later. He states (p. 106), ‘‘ La langue ou hypopharynx.. . 
est assez dévelopé chez tous les individus de la famille des Ephémérines, 
a exception du Prosopistoma, ot il est tres rudimentaire.” 

I shall not cite descriptions of the “hypopharynx”’ of additional in- 
sects, because I have nothing more to add, and the subject has been 
well treated of by Kolbe (90, pp. 213-217, Figuren 126-134), Packard 
(98, pp. 70-83, Figures 70-87), and others. Packard’s comparative 
account, in particular, is most excellent and well illustrated. (In his 
Figure 69, by the way, the abbreviations p. and hyp. should be inter- 
changed.) Briefly, the lingua is found in every order of insects, and 
although highly specialized in suctorial orders, retains, nevertheless, the 
same position and nearly the same relations to the salivary ducts that 
it does in the more generalized mandibulate orders which I have de- 
scribed. It is an interesting fact that in the Lepidopterous genus, 
Micropteryx, Walter (’85, Taf. XXIV. Figur 11) shows two hypo- 
pharyngeal stalks, readily comparable with those of Apterygota. 

The superlingue — which, as I have shown, originate quite indepen- 
dently of the lingua in Apterygota, but become more or less united with 
it in Orthoptera and Ephemerida — should hereafter be recognized as — 
morphologically important structures, and be searched for in even the 
most specialized haustellate orders as more or less intimate constituents 


FOLSOM : 


of the *‘ hypopharynx,’ 
lingua and “superlingu.” 


MOUTH-PARTS OF ANURIDA MARITIMA. 


117 


which term, then, may refer collectively to the 
The necessity for this new term, also 


brought out on page 132, will appear from the following synonymical 


table : — 
AUTHOR. APTERYGOTA. HYPoOPHARYNX. 
Lingua. Superlingue. 
De Olfers, ’62 Collembola lingua organa cochleariformia 
Meinert, °65 Thysanura tungen bitungens tvende Flige 
sc (trans.), °67 Thysanura lingua paraglossz 
Packard, ‘71 Collembola ~ eral is second maxille 
Tullberg, *72 Collembola lamina hypopharyngis laminz hypopharyngis 
inferior superiores 

Lubbock, ’73 Collembola and 

Thysanura ligula, lingua second maxillze 
Grassi, ’86 Thysanura ligula paragloss 
Oudemans, ’88 Thysanura ligula paragloss 
VY. Stummer-Traunfels, ’91 Collembola and 

Thysanura ligula paragloss~ 
Hansen, ’93 Collembola and 

Thysanura hypopharynx maxillulze 
Heymons, ’97 Lepisma hypopharynx 
Uzel, ’98 Collembola and 

Thysanura hypopharynx 
Folsom, ’99 Collembola glossa paraglossz 


Among Pterygota, the term “ hypopharynx ” of Savigny is fixed in 
application, although the compound nature of the organ is not gener- 
ally known. Synonymous with “hypopharynx ” are the following terms 
(see also Packard, ’98, p. 71): lingua (Savigny, 716), ligula (Kirby 
and Spence, ’28), langue ou languette (Duges, ’32), lingua (Westwood, 
*39, p. 9), tongue (Taschenberg, *79), hypopharynx (Dimmock, ’81 ; 
Burgess, ’80, and most others). 

“ Ligula,” ‘“glossa,” and “paraglosse” are terms established in 
Pterygota, but less fixed in the little-known Apterygota, and therefore 
more easily discarded in the latter group, as advised on pp. 132-133. 
* Maxillule ” and “second maxille” as applied to superlingue are un- 
fortunate because based upon unproved homological assumptions. The 
need for a new term, then, becomes evident. I have therefore suggested 
“ superlingue.” 

In Scolopendrella authors have omitted to mention whether the hypo- 
pharynx is present or not. 

Referring to Diplopoda, however, to which Scolopendrella is most 
nearly related, Packard (’98, p. 13) says, “The hypopharynx, our ‘ labi- 
ella’ (Figure 6), with the supporting rods, or stil linguales (sti. 1.), of 
Meinert, are of nearly the same shape as in some insects.” Latzel (Taf. 


IX. Figur 104; Taf. VL Figur 72) represents “ein Zwischenstiick der 
VOL, XXXVI.— NO. 5 3 


118 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


Zunge,’ for Lysiopetalum and Craspedosoma respectively, as well as 
two lateral lobes, or “‘ Zungenlappen ” (lobi linguales). These structures, 
although united with the gnathochilarium, are probably homologous 
with the separated lingua and superlingue of Apterygota, but, in the 
absence of the necessary embryological] investigations, that is all that 
may be aid. 

In the Chilopoda no structure analogons to the hypopharynx appears 
to be known. 

The “superlinguz ” of insects are homologous with the first maxille 
of Crustacea. In Anurida I have found (Plate 4, Figure 28, su’lng.) a 
distinct primitive ganglion — the fifth — for the superlingue, represent- 
ing the fifth, or first maxillary, ganglion of decapod Crustacea. This 


ganglion is eventually incorporated with the subcesophageal ganglion, 
and no superlingual nerves develop. Moreover, the superlingue origi- 
nate between the mandibles and so-called “ first maxille” of Anurida. 
The superlingnal fundaments, however, never become biramous — an 
exopodite or palpus does not appear —and are not segmented, like the 
Crustacean first maxille. In fact, they are much reduced structurally 
and functionally in Apterygota, and gradually reduced to disappearance 
in ascending the Pterygote scale. 

Hansen (93) regarded the superlingue +_ or “ maxillule,” as he termed 
them — from their position, as equivalent to the Crustacean first maxilla, 
emphasizing the opinion of v. Stummer-Traunfels (91) that the super- 
linguz bore palpi. The latter argument cannot be used, however, be- 
cause, as I show (p. 121), the palpi in question belong to the “ first 
maxille.” 

The lingua, usually termed “hypopharynx ” among insects, may easily 
be homologized with the hypopharynx of Malacostraca. It originates 
quite independently of the superlinguz as a median, unpaired papilla, is 
not supplied with a primitive ganglion or distinct nerves, and can no 
more be regarded as a distinct segment than can the labrum. In 
Orchesella and Anurida it finally becomes distinctly bilobed by a median 
groove, but the bilateral condition is clearly secondary. Packard’s evi- 
dence (’98, pp. 82-83) that the hypopharynx is “composed of, or sup- 
ported by, two bilaterally symmetrical styles both in Myriapods and in 
insects” has little weight, in view of what I have found to be the devel- 
opment of these “ lingual stalks.” 


The hypopharynx of insects, then, is a compound structure, the com- 


ponents of which originate independently. The median ventral lingua, 
like the labrum, does not represent a pair of appendages; the dorso- 


FOLSOM: MOUTH-PARTS OF ANURIDA MABITIMA. 119 


lateral “superlingue,” which have been usually overlooked or disre- 
garded in Pterygote insects, represent a distinct though reduced somite, 
as confirmed by the presence of a primitive ganglion. The superlinguz 
are homologous with the first maxille of Malacostraca, and are probably 
represented in Diplopoda. 

The lingua of insects is homologous with the Crustacean hypopharynx 
and probably with the median constituent of the gnathochilarium of 
Diplopoda. 


Maxille. 


The fundaments of the “ first maxille ” appear next after those of the 
mandibles, and at Stage 1 (Plate 1, Figure 1; Plate 2, Figures 8, 8a, 
mzx.') are a pair of small hemispherical papillz, similar to those of the 
mandibles. At Stage 3 they are longer than the mandibles and must 
consequently have lengthened faster. As seen in transections of the 
germ band, the maxilla is at first a simple ectodermal evagination, api- 
cally rounded, but at Stage 3 (Plate 3, Figure 15) the apex is flattened, 
and a lateral lobe, the beginning of the palp, has appeared ; this lobe is 
also seen in the ventral aspect of the germ band (Plate 3, Figure 11, 
plp.) as well as in the lateral views (Plate 2, Figures 9, 10). The pos- 
terior aspect of the left first maxilla when dissected out is given in 
Plate 3, Figure 17. 

At Stage 4 (Plate 3, Figures 12, 19) the maxilla has elongated con- 
siderably and its base is covered by the lateral fold of the germ band 
(Plate 3, Figure 19, pli. or.), as already mentioned. In the following stage 
(Plate 3, Figures 20, 21, mx.') the maxilla and palpus, though longer, 
are more nearly concealed by the lateral fold. The form of the maxilla 
with its palpus at this stage is shown in Figure 22, which was drawn 
from a dissection; the base of the maxillary fundament is already 
oblique, precisely as described for the mandibles, and the first maxille 
have begun to converge toward the median plane. It is to be remem- 
bered that the palpus is here a secondary lobe of the primary 
fundament. 

At Stage 7 (Plate 4, Figure 24; Plate 5, Figures 29, 30, ma.") the 
first maxillz, now covered by the lateral folds, have swung forward 
through an angle of almost ninety degrees (Figure 24), like the man- 
dibles. Claypole (98, p. 263) states that ‘a flexure of the embryo be- 
gins that results in crowding the mouth-parts together to form a definite 
head,” but such a purely mechanical interpretation will not serve, be- 


120 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


cause the paired mouth-parts are still at right angles to the germ band 
long after involution has occurred (Stage 5, Figures 5, 20). During 
this stage (7) the first maxille are attenuated toward their free ends ; 
a ventral view (Plate 5, Figure 29, mx.') shows their position in rela- 
tion to the lingua, and the extent of their convergence toward each other. 
The maxilla is quite unattached to the pharyngeal pocket (Plate 7, Fig- 
ures 44-50, cav. buc.) in which it lies, except where the margin of its 
basal aperture becomes confluent with the wall of the pocket (Figure 50) ; 
it has the form of a modified cone with an oblique, dorso-mesal, basal 
opening, as shown in transectious (Figures.44-50, mzx.1). The parts 
named stzpes and chitinous rod in my paper upon Orchesella are, as I 
have since found in that genus and in Anurida, distinguished simply by 
a greater deposition of chitin, and are connected above and below by 
delicate chitinized membranes, which I did not recognize until influ- 
enced by embryology to search for them. The “ chitinous rod,” then, is 
proved both by anatomy and development to be but a part of the 
stipes. 

During this stage (7) certain important differentiations of the first 
maxille are observable, if those organs are dissected out. The articula- 
tion between stipes and cardo (Plate 6, Figure 38, atc.) appears super- 
ficially as a notch, and in frontal section as a less chitinized region, 
as might be expected ; in a small hypodermal pocket is formed the stipal 
projection (Figure 38, pzj.) noticeable in the finished organ. The cardo, 
now transverse in position, was formerly the basal region of the lateral 
surface of the primary maxillary fundament, before the basal attachment 
became oblique. The articulation between the cardo and lingual stalk 
was described on page 112. 

In this stage, too, the head of the maxilla becomes vaguely separated 
from the stipes by a constriction (Plate 5, Figure 29). Later, the con- 
striction is more pronounced (Plate 4, Figure 25), and the apex of the 
head is fashioned inte an acute curving lobe, — the fundament of the 
galea (Plate 4, Figure 26, ga.) or “aussere Lade.”’ The “head ” is lined 
with a continuous layer of hypodermis cells. Next, on the mesal side 
of the head, a second lobe appears, the lacinia (/en.), or “ innere Lade.” 
Both galea and lacinia, then, become toothed on the mesal face, the 
teeth of the latter being produced each by a single cell ; the larger teeth 
of the former are secreted each by many cells. Eventually (Plate 6, 
Figure 39) the galea (ga.) becomes thickly chitinized except for a 
central hollow core, but the lacinia (/en.) remains thinly chitinized even 
in the adult. As in the mandibles, the hypodermis is finally excluded 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 121 


from the head of the maxilla, but through an opening in the constricted 
region nerve fibres may be traced to the lacinia. 

At this stage (7) the first maxillary palpus (Plate 5, Figure 30, p/p.), 
though still present, is no larger than it was in Stage 5 (Figure 22, plp.). 
In the newly hatched insect no trace of this palpus exists, hence it must 
have been resorbed. In the adult Orchesella, on the contrary, the 
palpus is functional and highly developed ; other facts also indicate that 
Anurida is a degraded form. 

Von Stummer-Traunfels (’91, p. 226, Taf. I. Figuren 6, 7), following 
Tullberg (’72, Taf. IV. Figur 17), observed a connection between the 
maxillary palpi and the so-called paraglossz of Collembola, and makes use 
of this union (p. 226) as the first of his reasons for recommending an im- 
proved designation of the mouth-parts, in the following words: “I. Die 
grosse Unwahrscheinlichkeit, dass der sogenannte Maxillartaster der Col- 
lembolen wirklich zur Maxille gehért, indem diese von jenem vollstandig 
getrennt ist und derselbe vielmehr in innigem Verbande mit den Para- 
glossen steht.” Hansen (’93, p. 209) uses this conclusion in proving 
that the ‘“paraglosse ” of Collembola and Thysanura are homologous 
with the first maxille of Crustacea. Without discrediting his conclu- 
sion, I have already shown (Folsom, ’99) upon anatomical data the 
trivial nature of the union between palpus and “ paraglosse” (super- 
lingue). I have now proved upon embryological evidence (Plate 3, 
Figure 22) that the palpus belongs to the maxilla, and have also shown 
(p- 114) that the chitinous membrane connecting it with the superlingua 
is simply incidental, and is only that part of the wall of the maxillary 
pocket which necessarily intervenes between the first maxilla and super- 
lingua of the same side. 

The fundament in Isotoma designated first maxilla by Packard (’71, 
Plate 3, Figure 13) is undoubtedly, from its position in relation to the 
first pair of legs, second maxilla; therefore what he regards in the same 
figure as a wnandible must be a first maxilla. Ryder (86) followed 
Packard in this matter, but Wheeler (’93, p. 57, Figure 6) shows the 
fundaments in their proper position. 

Claypole (’98) correctly identifies the first maxillary fundaments in 
Figures 43, 46, and 47, but does not mention the palpus. 

Uzel (’98) gives a figure of the first maxillary fundaments of Tomo- 
cerus and remarks (p. 36): ‘In jenem Stadium, bei welchem die Um- 
rollung des Keimstreifs vollendet ist, bemerken wir, dass sich die Anlagen 
des ersten Maxillenpaares (Taf. VI. Figur 87, mz.,) in zwei Hocker getheilt 
haben, und zwar in einen fusseren linglichen und in einen inneren 


1 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


stumpf dreieckigen. Der innere Hocker diirfte nach Analogie mit 
Campodea den lobus internus, der atissere die gemeinschaftliche Anlage 
des Lobus externus und des Palpus maxillaris vorstellen.” I entirely 
disagree with the author as to the interpretation of the lobes. In 
Anurida the lobus externus is not developed out of the palpal lobe of 
the biramous fundament, but the remaining lobe is the common funda- 
ment of lobus externus and lobus internus. Therefore Uzel’s foot-note 
on page 36, “An den Maxillarpalpen von Macrotoma (Tomocerus) vul- 
garis fand ich selbst einen kleinen Vorsprung, der wohl als Lobus ex- 
ternus zu deuten ist,” etc., is open to criticism; the minute papilla to 
which he refers is precisely like several other papille distributed upon 
the palpus (see Folsom, ’99, Plate 3, Figure 18, p/p.), except for a trifling 
difference in size. It is very doubtful if a difference in this matter exists 
between Anurida and Tomocerus, especially since the process as observed 
by me agrees with that of insects in general, as far as is known, excepting 
possibly Lepisma, presently to be noticed. 

Uzel applied to Tomocerus conclusions drawn from Campodea, in 
which he (’98, pp. 33-34, Taf. VI. Figuren 79, 80) derives the galea 
from the palpal lobe. His diagrams, unfortunately, do not elucidate 
the basal relations of the three principal lobes: palpus, galea, and 
lacinia. 

The completed first maxille of Campodea (Meinert, ’65, Taf. XIV. 
Figuren 17, 18; Grassi, 86°, Tav. IV. Figure 2, 13; v. Stummer- 
Traunfels, 91, Taf. I. Figuren 5, 11) are remarkably like those of Col- 
lembola (Folsom, ’99, Plate 3, Figures 18-21): the cardo is articulated 
to the superlingual stalk in the same way; the hollow stipes, distinct 
head, galea, and lacinia are also alike, and resemble less the homologous 
parts of Pterygote insects. The solid bifid galea and the fringed seven- 
lobed lacinia of Campodea, as I call them, are by Grassi and v. Stummer- 
Traunfels regarded collectively as the “innere Lade” or lacinia. The 
latter author says (p. 223), ‘ Man kann daher bei den drei vorliegenden 
Formen eine successive Riickbildung des Aussenladens annehmen. Bei 
Japyx noch zweifach gegliedert, ist er be1 Campodea schon mehr reducirt 
und fehlt bei den Collembolen giinzlich.” It is curious to observe how 
authors have followed one another in deriving the galea from the palpal 
fundament. I have shown in Anurida (anticipating later conclusions) 
that the galea and lacinia both originate from the “ endopodite” of the 
bifid fundament. a 

Japyx, of course, agrees substantially with Campodea. The second 
maxilla, however (Meinert, ’65, Taf. XIV. Figuren 8, 9; Grassi, ’g6°, 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 123 


Tay. IL. Figure 2, 3, 6,8; v. Stummer-Traunfels, ’91, Taf. I. Figuren 
4, 10) has a two-lobed galea and a four-lobed lacinia. 

In Japyx, thanks to Meinert’s figure (65, Taf. XIV. Figur 8), the 
muscles may be clearly homologized with those I (99, Plate 3, Figures 
20, 21) have described for Orchesella. As Meinert did not designate 
the muscles, I can simply say that they severally correspond with those 
labelled by me 3. add., 4. add., 10. add., 7. add. or 9. pr’t. add., and one 
muscle with both 4. pr’t. add, and 6. prt. add., while one of two others 
probably represents 8. ret. add. 

In Lepisma, according to Heymons (’97°, p. 592, Taf. XXX. Figuren 
13, 15, 17, 20), the fundament of the first maxilla forms the pal- 
pus, at the base of which appears a mesal lobe, which itself divides 
to form galea and lacinia. This account is, then, at variance with mine 
on Anurida, that of Uzel on Campodea, and that of Ayers for the Orthop- 
teran genus (Ecanthus, and is, so far as I know, unsupported by the re- 
sults of other authors. In fact, Figure 13 of Heymons even suggests 
that the palpus is a lateral lobe of the primary fundament, as I have 
found it to be in Anurida. As to the origin of the three first maxillary 
lobes, Uzel, Heymons, and myself disagree, as I have said. Uzel’s 
account agrees with mine, in so far as he makes the palpus a lateral 
evagination of the primary, or stipal, fundament ; and Heymons, like 
myself, derives both lacinia and galea from the inner lobe of a biramous 
appendage. 

In its final form, the first maxilla of Lepisma is easily recognized as 
homologous with that of other Thysanura, but approaches remarkably 
the same organ in Orthoptera, especially that of the Blattide. As in 
other Apterygota, the stipes (v. Stummer-Traunfels, ’91, Taf. II. Figur 
11; Muhr, ’77, Taf. VII. Figur 45) has a basal opening, cardo, distinct 
head, galea, and lacinia, and the origin of the muscles (Oudemans, ’88, 
p. 187) “findet man auch hier an Chitinstiicken im Kopfe.” The 
palpus in Lepisma, however, is five-jointed, as in Orthoptera. What I 
call galea and lacinia are also, in this particular case, named “ Aussen- 
lade” and “ Innenlade” by v. Stummer-Traunfels. 

Machilis is nearer than Lepisma to Campodea and Collembola in the 
structure of the first maxille. As may be seen from the figures by 
Oudemans (’88, Taf. II. Figur 27) and v. Stummer-Traunfels (’91, 
Taf. II. Figuren 8, 9, 10), the positions of the cardo, stipes, galea, 
lacinia, and palpus are exactly comparable in the three groups. The 
palpi in Machilis, to be sure, are seven-jointed, and a palpiger is present, 
as in Orthoptera, The structure identified by v. Stummer-Traunfels as 


124 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY, 


“ Aussenlade” in Machilis, cannot be homologous with the part bearing 
the same name in other insects, for in Machilis it is clearly a part of the 
palpiger instead of being a constituent of the head of the maxilla. The 
two adductor muscles described by Oudemans (’88, Taf. I. Figur 19) 
as extending from the inner wall of the maxilla to a median tentorium, 
are probably the homologues of 3. and 6. pr’t. add. of Orchesella (Fol- 
som, 99, Plate 3, Figure 20). 

In CEcanthus, Ayers (’84, p. 241, Plate 18, Figures 20-22; Plate 19, 
Figure 5) has traced the development of the first and second maxillz as 
far as the trilobed condition, his ideas (p. 241) agreeing with mine on 
Anurida: “ The primitive appendage is first divided into two lobes, and 
the inner of these becomes secondarily divided into two.” Patten (’g4, 
p- 596) says, “A rather striking variation was found in the first and 
second maxille of Blatta, which were formed respectively of two and 
three lobes.” Wheeler (’89, p. 348) adds, regarding the same genus, 
“The outer of the three lobes of each maxilla becomes the palp, while the 
inner two become the galea and lacinia of the adult.” Heymons (95°, 
p- 19) states that in Forficula, “drei selbstandige Aeste zu erkennen 
sind, aus denen Lobus internus (lacinia), Lobus externus (galea) sowie 
der Palpus hervorgehen.” This trilobed stage is exactly comparable 
with that of Lepisma, although Heymons and Ayers differ as to its 
derivation. 

Although Wood-Mason (79) emphasizes the agreement between 
Machilis and Orthoptera, I may say that Lepisma is intermediate 
between the two in structure, with decidedly orthopteran affinities. 
Especially is this true of the first maxille. The cardo, stipes, galea, 
lacinia, and palpus of Lepisma (Muhr, *77, Taf. VII. Figur 45, or v. 
Stummer-Traunfels, ’91, Taf. II. Figur 11) not only agree in position 
with those of Blatta (Muhr, ’77, Taf. II. Figur 12, or Packard, 83%, 
Plate XXVIII. Figure 12, Periplaneta), but exhibit a surprising agree- 
ment in form, as well as the number of palpal segments ; in both groups, 
also, a palpifer is differentiated. Through Lepisma, therefore, the first 
maxille of Collembola may be homologized with those of Orthoptera, 
and hence all other Pterygote orders. I have traced the homologies, 
part for part, between Lepisma and all the families of Orthoptera, as 
well as the genera Ephemera, Myrmeleon, and Corydalus, in which lat- 
ter genera the nymphal first maxillee are but little specialized in form. 
Heymons (’96, p. 19) states that in the Libellulid genus Epitheca, 
‘“‘Erst spéter gliedert sich von der Aussenseite der Maxille eine kleine 
rundliche Erhebung ab, welche die Anlage des Tasters darstellt (Figur 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA, 125 


19, palp. mzx."), wihrend das in der directen Fortsetzung des urspriing- 
lichen Maxillen-Zapfens liegende Endstiick zur Lade (lobus) wird.” This 
agrees with Anurida, Campodea, and (Kcanthus, but disagrees with the 
account given by Heymons himself for Lepisma. 

Turning to the Myriopods, Scolopendrella, while undoubtedly more 
closely allied to the Diplopods, nevertheless shows in many ways inter- 
esting correspondences with Campodea, as other writers have already 
stated. The lateral parts of the plate termed the “ gnathochilarium ” 
resemble in several respects the first maxillee of Campodea. According 
to Latzel (84, Taf. I. Figuren 6, 7) and Grassi (’86*, Tay. II. Figure 
5, 10), there is an elongated hollow stipes bearing an outer (galeal) 
and also an inner (lacinial) terminal lobe, both of which agree in detail 
with the comparable structures of Campodea and Japyx; for in Cam- 
podea, a one-jointed palpus is present, and in Campodea, Japyx, and 
Collembola, a “ chitinous rod” extends backward from the lacinia. 
The few muscles shown by Latzel (’84, Taf. I. Figur 7) are to be 
compared with 5. and 6. pr’t. add., and 8. ret. add. of Orchesella (Fol- 
som, ’99, Plate 3, Figures 20, 21). Grassi (86%, p. 16) states that 
muscles from within the organ pass to an endoskeleton, which, as one 
may see from his Figure 25, is essentially like the “ lingual stalks ” 
that I have found in Orchesella and Anurida, and still more nearly like 
the same structure of Campodea and Japyx. All these similarities 
confirm the view, based primarily upon other anatomical data, that 
Scolopendrella most clearly represents the hypothetical ancestor of 
insects. 

Among Diplopods the passage from the more generalized genera, as 
Lysiopetalum or Craspedosoma, ‘to Scolopendrella is clear. In the first 
genus, especially, are seen a cardo (not described as yet for Scolopen- 
drella), stipes, galea, and lacinia, all simple in structure, but no palpus. 
I should state, however, that it remains to confirm these homologies by 
embryology. 

In Campodea the second pair of jaws is usually homologized with 
the first maxille of Insects; but, except in position, there is little re- 
semblance between the two organs. 

The first maxille of insects are usually homologized with the first 
maxille of Crustacea, but if, as I maintain, the “superlingue” are 
equivalent to the latter organs, it follows that the hexapod first maxille 
correspond to the Crustacean second mavxille. 

The primitive biramous character of Crustacean mouth-parts is well 
known, and Hansen (’93, p. 198) has, in connection with this subject, 


126 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 


formulated a significant law — “dass man drei Glieder im Stamm von 
allen gespalteten Gliedmassen bei den Crustaceen als ein primares 
Verhiltniss annehmen muss, und diese Zahl hat sich, wenigstens in 
den angefiithrten Fiillen, deutlich erhalten.” In fact, Hansen himself 
(p. 206) has homologized the first maxillz of Machilis with the second 
maxilla of Crustacea, on account of the three axial segments and the 
position of the palpus, saying: “Der Bau der Maxillen . . . stimmt 
also genau mit den Maxillen der Eumalacostraken.” 

The axial segments of the Crustacean appendage are on this view 
successively equivalent to cardo, stipes, and palpifer of Hexapoda. 

It must be admitted that these anatomical agreements, if appealed to 
alone, may logically be used to support other views than my own, since 
all the Crustacean appendages are constructed upon the same plan; but 
the equivalence of the neuromeres in Hexapoda and Crustacea is a mat- 
ter of the greatest significance. Viallanes has proved that the first three 
neuromeres in the two groups agree in great detail, and I find that his con- 
clusions apply equally well to the succeeding neuromeres, It is very sig- 
nificant that in most cases the appendages of equivalent somites have 
the same function in the two groups, and that all the paired nerves of 
the head in Collembola agree exactly in position with those of decapod 
Crustacea. 

Summarizing: The first maxille of Apterygota develop in all essential 
respects like those of Orthoptera, with which they may be homologized 
in detail. In Anurida a palpus appears, but is resorbed before hatching, 
indicating the descent of Anurida from a form in which the first maxil- 
lary palpi were functional. The first maxillee of Campodea are clearly 
to be homologized with those of Scolopendrella, and less clearly with 
the lateral portions of the Diplopod gnathochilarium. The first maxillee 
of Hexapoda pass through a biramous stage, such as obtains among 
Crustacea, are comparable with Crustacean second maxille in some 
detail, and are homologous with those of Malacostraca. 


Labium. 


The fundaments of the labium, or “second maxille,”’ appear next 
after those of the first maxille, and at Stage 1 (Plate 1, Figure 1; 
Plate 2, Figure 8, mx.) are a pair of simple conical elevations rising 
perpendicularly from the germ band and slightly longer than the funda- 
ments of the mandibles and first maxille. In the following stage (2) 
they are longer and more cylindrical (Figure 2); in Stage 3 (Figure 3) 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 12 


they are somewhat larger, and ventral or lateral surface views of the germ 
band (Plate 2, Figures 9, 10 ; Plate 3, Figure 11) disclose a distinct lateral 
lobe, the palpus (p/p.), which is larger than that of the first maxilla. 
A second maxilla, as dissected out at this stage, is shown in Figure 18 
(Plate 3). Transections of the germ band (Plate 3, Figure 14) show 
the palpus to be an outfolding of the antero-lateral face of the primary 
maxillary evagination, just as in the case of the first maxilla. 

At this stage (Plate 2, Figures 9, 10) there appears near the mandibles 
a lateral evagination (pl. or.) of the germ band, destined to form the 
side of the face; this fold grows backward until it involves the base of 
the second maxilla of the same side, and the internal cavities of the two 
folds become one. In Stage 4 (Figure 4; Plate 3, Figure 19) it has 
already involved the base of the second maxilla; the apex of the maxilla, 
however, is still free from the fold, and the palpus (Plate 3, Figure 12, 
plp.) is as large as that of the first maxilla. 

At Stage 5 the second maxille (Figure 5; Plate 3, Figure 20, mz.*) 
are long, oval in cross-section, and project at right angles to the germ 
band; the antero-lateral region of the base is confluent with the mouth- 
fold (Figure 21). At this period all trace of the second maxillary palpus 
becomes lost ; it has not become involved in the mouth-fold, which is 
still restricted to the base of the maxilla, but has been rapidly resorbed 
and appears at last as indicated in Figure 20. In the next stage (6) 
the second maxille (Figure 6) converge toward the median plane like 
the other pairs of oral organs, and similarly swing forward. 

At Stage 7 (Plate 2, Figure 7) the second maxillze and mouth-folds 
are quite confluent (Plate 5, Figures 30, 34), but the anterior part of 
each maxilla is still distinguishable as a swollen lobe, or less flattened 
region (Plate 4, Figure 24, /ab.). The bases of the second maxille, 
although widely separated in Stage 5 (Plate 3, Figure 21, mzx.”), sub- 
sequently spread toward the median plane, become thinner, and gradually 
form a single plate; the median sinus between them shortens until the 
condition shown in Plate 5, Figure 29 (/ad.) is attained. The union of 
the second maxille with each other is not a simple contact and_fusion 
resulting in a median suture ; but a confluence of the cavities of the two 
maxille occurs and progresses forward (7. ¢., distally), ceasing, however, 
before obliterating the median sinus, which remains in the adult (Plate 
7, Figures 43, 45, swt. m.and swl.). Although the finished labium bears 
a median ventral groove, the groove does not indicate the fusion of the 
fundaments; at Stage 7, when the labial plate is complete, no trace 
exists of the groove, which is formed in a later stage. A comparison of 


128 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


my figures (Plate 3, Figure 20; Plate 5, Figure 29) will show that 
practically the entire ventral surface of the head is labial in origin, be- 
cause the original bases of the second maxillz extended quite to the first 
pair of legs; an inconsiderable, if any, portion of the germ band inter- 
vening (Figure 21) between them. 

At Stage 8 the mouth is nearly closed (Plate 5, Figure 34) by the 
overgrowth of the combined second maxillz and mouth-folds. 

In the adult (Plate 7, Figure 43) the apical lobes, although in con- 
tact mesally and stoutly chitinized, are readily separable and may be 
depressed and elevated by muscles homologous with those of Orchesella, 
the hinge lines being shown at sut. Shortly before hatching, hypodermis 
cells evaginate singly to form the external setz of the head. 

In the development of the labium, as I have traced it, neither galea 
nor lacinia becomes differentiated ; but the terminal lobe is equivalent 
to the head of the first maxilla, and therefore represents the common 
fundament of galea and lacinia, the second maxilla not passing the 
biramous stage. All of the labium behind the terminal lobe represents 
not only the stipes and cardo of the first maxilla, but also the mentum, 
submentum, and gula of the Orthopteran labium, —an important 
conclusion. 

In Orchesella (Folsom, ’99, Plate 3, Figure 24) mentum, submentum, 
and gula appear to be indicated, but the development in Anurida throws 
no light upon the structures which I suggested might be modified palpi. 

Packard (’71, p. 17) in describing Isotoma says, “I was unable at 
this or any other period to discover any traces of the second maxille. 
Though existing in a very rudimentary state in the adult, I could not 
detect them after repeated attempts, but do not doubt but that a more 
skilled observer would have made them out. Indeed, it is a most diffi- 
cult thing to discover their rudiments in the adult ; I failed, at the time 
these observations were made, to detect them, though since then I have 
succeeded in making out their structure and relation to the surrounding 
parts of the mouth.” Asa matter of fact, he (Plate 3, Figure 13) has 
evidently figured the second maxille, which I know to be present in the 
genus, and in the passage quoted he doubtless referred to the super- 
lingue (“ paraglosse ”), which Lubbock also #73, p. 66) termed “second 
maxille.’’ Ryder (’86, Plate XV. Figures 7, 9, 10), too, repeated the 
mistake in Anurida. 

Claypole (98, Plate XXIII. Figures 40-44, 46, 47) represents the 
fundaments as simple papille without distinguishing the palpi, which 
are, however, obscurely indicated in Figures 43 and 47. 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 129 


Uzel (’98, Taf. VI. Figur 87) shows the papillz of the second maxillee 
in Tomocerus. Concerning the development of the second maxillz in 
Campodea, he (’98, p. 33) says, “Auch an den Anlagen der zweiten 
Maxillen (Taf. IV. Figur 38 und Taf. VI. Figur 79, mz.,) lisst sich ein 
kleinerer lateraler und ein grésserer medialer Theil unterscheiden, die 
indess nicht scharf von einander gesondert sind.” .. . (p. 34) “Anden 
Anlagen der zweiten Maxillen tritt auf der Mitte des Hinterrandes. ein 
Vorsprung auf (Fig. 80, e,), aus welchem sich, wie wir voraussenden 
wollen, der Lobus externus entwickelt, wogegen der friiher besprochene 
innere Theil den Lobus internus (/,) und der d&ussere den Palpus 
labialis (pmz,) aus sich entstehen lasst. Zugleich bemerkt man an 
den beiden Maxillenpaaren eine gewisse Rotation. Die éusseren Enden 
derselben bewegen sich néimlich nach vorn (Fig. 80), so dass die beiden 
Anlagen eine schriige Stellung erhalten. Bald jedoch, und zwar in dem 
Stadium, wo die vollkommene Umrollung des Keimstreifs zustande 
gekommen ist (Fig. 41), kehren sie in die urspriingliche Lage zuritck 
(das erste Maxillenpaare nicht ganz), und es erfolgt nun eine Rotation 
des zweiten Maxillenpaares allein im entgegengesetzten Sinne; die 
tinsseren Enden desselben bewegen sich nimlich jetzt nach hinten und 
drehen die ganze Anlage in eine entsprechende schrége Lage, welche 
aus Fig. 81 ersichtlich ist. 

“Tm ndchsten Stadium (Fig. 82) . . . die Anlagen des zweiten Max- 
illenpaares haben eine dreilappige Gestalt angenommen. Die drei Lap- 
pen lassen sich leicht deuten, wenn man die vorhergehenden Stadien 
vergleicht. Der vorderste (/,) entspricht dem Lobus internus, der 
mittlere (/e,) dem Lobus externus, und der hintere, breit gerundete 
(pmz,) stellt den Palpus labialis vor. Auch bemerken wir, dass sich 
nach der erwihnten Rotation die beiden Anlagen des zweiten Maxillen- 
paares einander stark in der Medianlinie geniihert haben (Fig. 82) und 
auch etwas nach vorn geriickt sind.’ ‘In den nichsten Stadien (Fig. 
83 und 84), bei welchem der Keimstreif schon etwas spiralig gerollt er- 
scheint (Fig. 42), riicken die Anlagen des zweiten Maxillenpaares noch 
niher aneinander, und zwar ganz besonders die Lobi interni (/¢.).” In 
the postembryonic stage (p. 47): ‘Die beiden Anlagen des zweiten 
Maxillenpaares riicken in der Mittellinie noch niaher als frither zusam- 
men, so dass nicht nur die Lobi interni (/imz.), welche sehr gross 
geworden sind, sondern auch die Lobi externi (/ema,) dicht neben 
einander zu liegen kommen. Eine Verwachsung der beiden Hialften des 
zweiten Maxillenpaares findet jedoch auch beim erwachsenen Thiere 
nicht statt.” 


130 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


It is not clear, then, whether the galea develops from the outer or 
the inner lobe of a biramous appendage, although Uzel’s account is, at 
least, not inconsistent with his description of the first maxille, which I 
have already criticised. Although Uzel does not state as much, his 
figures indicate the palpus to be an appendage of the primary funda- 
ment, as it is in Anurida. In this genus, however, no third branch ap- 
pears, as I have said; but, from analogy with the first maxilla, the inner 
of the two branches represents undifferentiated galea and lacinia. 

The rotation in a frontal plane of the second maxillary fandament of 
Campodea — which does not occur in Anurida— enables me to homo- 
logize the finished labium of Campodea with the apparently different 
labium of all other insects. If Uzel’s figures are compared with Figure 
12 of y. Stummer-Traunfels (91), it is easy to see that the embryonic 
structures by Uzel designated lim, (lacinia), Jem, (galea) and pmax, 
(palpus) are with hardly a doubt respectively represented in the adult by 
the parts which v. Stummer-Traunfels termed up. (“untere Mundplatte”), 
pl. (‘‘tasterformige Papille”) and pp. (‘‘ Tastwarze”’). These homo- 
logies, however, could never have been settled upon merely anatomical 
grounds. 

What Grassi (86°, Tav. IV. Figura 3), then, considered to be the 
under lip (/a. a.) of Campodea is but the anterior part of the true 
labium; the “labial palpi” (pa. lz.) are really galee borne upon a 
region representing the mentum, and the “labial papille” (pa. da.) 
are but modified palpi. As in Collembola, the labium is anteriorly and 
deeply cleft. 

Japyx is so close to Campodea that the same conclusions may doubt- 
less be applied to both genera. In Japyx the labium, as in Collembola, 
is split and bears a median sulcus (Grassi, 86°, Tav. III. Figura 21) 
much like that of Orchesella (Folsom, ’99, Plate 4, Figure 29). Ex- 
amining Figure 1 of v. Stummer-Traunfels (’91, Taf. II.), the lacinia and 
galea are clearly represented, as in Campodea; the true palpus, however, is 
but obscurely differentiated in the region behind the so-called palpus (pl.) 
and nearer the median plane. The eversible papillee of the anterior part 
of the labium, as described by Meinert (67, p. 369) and Grassi (’86°, 
p- 31), are probably homologous with the papille of Orchesella which I 
designated pip. (’99, Plate 3, Figure 24). 

For Lepisma, Heymons (97°, p. 590, Figur 11) gives, first, a pair of 
simple second maxillary fundaments and later (Taf. XXX., Figur 20) a 
long palpus with a small, basal, inner lobe, and states (p. 592) “Die 
Lobi oder spateren Ladentheile der Maxillen sind in diesen Stadien erst 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA, 131 


als sehr kleine unscheinbare Vorspriinge erkennbar, welche medialwarts 
an der Basis der Taster hervorwuchern.” This is contrary to the condi- 
tions in Anurida, where the palpus is certainly itself an outgrowth from 
the siraple, primary papilla (Figure 13). Lepisma agrees with Anurida, 
however, in that the galea and lacinia are derived from the inner lobe of 
a biramous fundament (Heymons,’ 97°, Taf. XXX. Figur 17), and dis- 
agrees with Campodea if, in the latter genus, as Uzel implies, the galea 
buds from the palpus. The finished labium of Lepisma, as I shall show, 
is remarkably like that of Orthoptera. 

The labium of Machilis, as described by Oudemans (’88, pp. 185-186, 
Taf. II. Figuren 28, 29), resembles that of Campodea and Collembola in 
being deeply cleft, and having the salivary ducts opening in similar posi- 
tions, but it more nearly approaches the Orthopteran type in the position 
and structure of the terminal lobes, the mentum, and the three-jointed 
palpi. Each terminal lobe is subdivided into four lobes, which in all 
probability collectively represent galea and lacinia. 

Ayers (84, p. 241, Plate 18, Figures 20-22; Plate 19, Figure 5), as 
already quoted (p. 124), has traced the development of the second maxille 
of Gicanthus as far as the trilobed stage, stating the lobation to be more 
prominent in the second than in the first maxillary appendage. The 
fact that the second maxille of Anurida develop upon the Orthopteran 
type is important. In Lepisma, the trilobed fundaments agree with 
those of Orthoptera even as to the greater length of the palpus. 

In the finished labium of Cicanthus (Packard, ’83*, Plate XXVII. 
Figure 9) the derivatives of each trilobed fundament are easily identified 
as three-jointed palpus, galea, lacinia, palpifer, and mentum, — the last 
two structures having doubtless arisen from the common stalk, or stipes. 
Although the labium is constructed upon the same plan in all Orthoptera, 
we may best select Blatta for comparison with Lepisma. The agreement 
between Blatta (Mnhr, 777, Taf. II. Figur 11; Packard, ’83*, Plate 
XXVII. Figure 14) and Lepisma (Muhr, ’77, Taf. VIII. Figur 46; 
v. Stummer-Traunfels, ’91, Taf. II. Figur 17) is surprising. Galez and 
lacinize clearly correspond in the two, as do the mentum, palpifers, and 
palpi, the last, however, having three segments in Blatta and four in 
Lepisma. Muhr, in fact, included Lepisma among Orthoptera, as have 
some other authors. 

It is now agreed that the first and second maxille of Orthoptera are 
homodynamice, and, more inferentially, that the same is true of other in- 
sects. The exact agreement first recognized, according to Packard (98, 
p- 69), by Miall and Denny (’86), was detected long before, at least, by 


132 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 


Muhr (77, p. 9) and by Schaum (’61, p. 84). In Anurida the whole gular 
region, excepting the terminal lobes and palpi, represents the undifferen- 
tiated gula, submentum, mentum, and palpifers; therefore the gula in 
Orthoptera may be regarded as the united cardines, and the submentum, 
mentum, and palpifers, as stipal derivatives. It will be seen that my view 
differs from those accepted and defended by Packard (’98, p. 69) and 
others; but it is supported by embryological evidence, while the other 
views are not. It may safely be predicted that the apparently unpaired 
gula of Orthoptera will be shown to originate from paired fundaments, 
as I have found it to do in Anurida. 

If these homologies between Collembola, Thysanura, and Orthoptera 
are accepted, their extension from the last group to other Pterygote 
orders is not difficult, even though the desirable emibryoleen verifica- 
tions are still wanting. 

There is an unfortunate confusion of terminology regarding the mouth- 
parts of insects. The homologies are much obscured, but less by the 
use of different terms for homologous parts, than by the use of the same 
name for parts which are not homologous. “ Paraglosse” and “ligula” 
are cases in point. To most entomologists “ 
ently the labial lobes homodynamie with the gale and the laciniz of 
the first maxillee, or else mean the galeal lobes alone, while “ ligula ” 
“olossa’”’ signifies the lacinial lobes, often more or less fused into a 
median organ; in fact, “ligula” is often used synonymously with 
“labium ” in reference to many Coleoptera (Le Conte and Horn, ’83, 
p- xviii). “Ligula,” however, is often made a synonym of “lingua” 
(Packard, ’98, p. 68), and the latter term, of “hypopharynx.” In my 
opinion, the term “lingua” should be restricted to the median, un- 
paired constituent of the hypopharynx ; for the “ hypopharynx ” of cer- 
tain insects often bears two dorso-lateral lobes which in more generalized 
insects are not only free from the lingua, but quite distinct from it in 
origin (as proved by myself in Anurida and by Uzel in Campodea), and 
these dorso-lateral appendages are most frequently called “ paraglossz,” 
upon assumptions which are not sustained by embryology, as I shall 
presently show. = 

As the terms “ paraglosse ” and “ ligula,” or “ glossa,” are irremoy- 
ably fixed, as applied to labial structures, they should not be used for 
anything else. It is both unnecessary and impossible to displace the 
term “hypopharynx,” but it is necessary to recognize the overlooked 
fact that the “ hypopharynx” is frequently a compound organ, to the 
ventral and median component of which the term “lingua” may weil 


paraglossee ” mean indiffer- 


9 


co) 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 133 


be restricted ; while, for the dorso-lateral appendages, rejecting “ para- 
glossve,” I propose the more appropriate name “ superlingue.” 

The “gnathochilarium” of Symphyla and Diplopoda may also prove 
to be in part homologous with the hexapod labium. Having already 
discussed the resemblances between the lateral portions of the gnatho- 
chilarium and the first maxille, I may compare the median components 
with the labium. They were, in fact, designated “under lip” in Sco- 
lopendrella by Grassi (’86*, Tav. II. Figura 5). As in Apterygota, there 
is a median portion and two stipal plates, each of which bears a papil- 
late head, separated by a transverse suture. These are the only 
points of agreement. On the contrary, the gnathochilarium is usually 
homologized with the first maxillee of insects (Packard, ’g3°, p. 199; 
Korschelt u. Heider, 90-93, p. 906) —apparently on account of Met- 
schnikoff’s (74) researches. I can only-suggest that the under lip of 
Diplopods is anatomically of too compound a nature to be homologized 
with the first maxillz only, and that we are not warranted in deriving 
the entire lip from only two primary fundaments simply because Met- 
schnikoff did not allude to more than two. In fact, Heymons (’97, p. 7, 
Figur 2) has discovered a “ post-maxillary” segment, without append- 
ages, in the embryo of Glomeris ; but he regards it as equivalent to the 
labial segment of insects. In other Diplopoda, for example Lysiopetalum 
(Latzel, 84, Taf. IX. Figur 104) and Craspedosoma (Latzel, ’84, Taf. 
VL. Figur 72), the structure of the under lip is remarkably like that in 
Scolopendrella. 

In Chilopoda there are two fleshy, jointed appendages (“first maxilli-- 
pedes,” “zweites Unterkieferpaar”), which are conceivably equivalent, 
in position only, to the second maxilla of Hexapoda, and are generally 
homologized with the first pair of legs of Diplopoda. If the second 
maxillz of insects are represented among Diplopoda in the manner I 
have suggested, then the second pair of Chilopod “ maxillipedes ” 
(“ Kieferfusspaar””) corresponds with the first pair of feet of both 
Diplopoda and Hexapoda, —a simple conception. 

The labium of Hexapods is homologous with the first pair of maxilli- 
peds of Crustacea, according to the homologies which I have already 
proposed for all the more anterior paired appendages. It is, then, erro- 
neous to homologize with each other the second maxille in these two 
classes; but the error is so firmly established that I have in this paper 
frequently employed the term “second maxille” for the labium of 
insects, in order to avoid confusion. 


The evidence for my view of the homologies of the labium is of the 
VOL. XXXVI. — NO. 5 4 


134 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 


same character as that already used for the ‘ first maxille.” The labial 
fundaments are appendages of the seventh somite in both Hexapods and 
Crustacea and are supplied by equivalent ganglia and nerves. In both 
groups each fundament is at first simple and secondarily develops a 
palpus, or exopodite. Moreover, the axis of the appendage is three- 
segmented, the segments in Crustacea corresponding to gula, mentum, 
and palpifers of generalized Hexapoda, the submentum being a secondary 
development. 

Hansen (93, p. 206) differs slightly: “ Das Submentum [Machilis] 
ist mit dem, bei den Gammarinen zusammengeschmolzenen ersten Gliede 
homolog, das Mentum mit dem bei den Hyperinen auch zusammenge- 
schmolzenen zweiten Gliede ; anf der Spitze des Mentums findet man ein 
Glied, das auf jeder Seite in vier Laden ausgeht, die, wie sich ziemlich 
deutlich zeigt, zwei Laden angehGren, die jede fiir sich gespalten ist, und 
diese halte ich (unter Anderem wegen eines Vergleiches mit Orthoptera 
und Amphipoda, kann aber keinen zwingenden Beweis von den Skelet- 
theilen fiihren) respectiv fiir eine Lade vom zweiten Gliede (die innerste 
gespaltene Lade) und fiir das dritte Glied des Labiums mit seiner ge- 
spaltetem Lade; der Palpus geht von der Aussenseite des dritten Gliedes 
aus.” 

Hansen should have taken into consideration the gula, and the fact 
that the submentum is probably not a primitive sclerite. 

The homologies between Hexapoda and Crustacea that I have defended 
are none the less valid if the total number of somites differs in the two 
classes, and they are sustained if the number is the same. In decapod 
Crustacea there are twenty-one somites, including the ocular segment. 
In generalized insects the number of abdominal segments varies. In the 
embryo of Lepisma, which shows marked affinities with Crustacea and 
Orthoptera, Heymons (97%) finds eleven abdominal somites. Add to 
these the thoracic segments and the seven which I have found in the 
Apterygote head; and the total, twenty-one, is the same as for decapod 
Crustacea. In embryos of many families of Orthoptera and Odonata 
just eleven abdominal segments are present. On the other hand, 
Heymons (’95°) has found twelve in certain genera of the same orders, 
and in Collembola the number varies greatly. In view of this variability 
within the limits of the same order, then, it is well not to emphasize the 
agreement between generalized insects and decapod Crustacea in the total 
number of somites. 

My conclusion regarding the labium, then, is that its development in 
Apterygota conforms to the Orthopteram type. In Anurida a labial pal- 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA, 135 


~~ 


pus is formed and resorbed, — an indication of degeneracy. The entire 
gular region of Apterygota is labial in origin; but fewer sclerites are 
differentiated than in Pterygote insects. The labium of insects is homo- 
dynamous with the “first maxille ” and homologous in detail with the 
first mavxillipeds of decapod Crustacea. The labium of Campodea is 
equivalent to the “‘second maxille ” of Symphyla, and is represented in 
the Diplopod gnathochilarium. 


Skull. 


The principal mouth-parts of Collembola, unlike those of all other 
insects, except certain Thysanura, are internal; the way in which they 
become so will now be described. 

The beginning of the process is seen at Stage 3 (Plate 1, Figure 3), 
when the ventral surface of the germ band is almost flat. In lateral 
aspect (Plate 2, Figures 9, 10) the edge of the germ band is produced 
downward as a small crescentic lobe (pli. or.) outside the fundaments 
of the mouth-parts. This lobe usually originates on the mandibular 
segment, as represented in Figure 9, but may arise more anteriorly, as 
in Figure 10. These figures represent, respectively, the left and right 
sides of the same individual. Rarely, the lobe begins behind the man- 
dible. A transection of the germ band near the middle of the lobe 
(Plate 3, Figure 16) proves the lobe (plz. or.) to be an evagination of 
the ectoderm enclosing mesoderm. In ventral aspect at this stage 
(Figure 11) the mouth-fold is clearly distinguishable at its widest part, 
or place of origin, but gradually disappears anteriorly and posteriorly on 
account of its confluence with the rest of the germ band. 

At Stage 4 (Plate 1, Figure 4) and a little later, while involution of 
the germ band is occurring, the mouth-fold is considerably larger (Fig- 
ures 12, 19, plz. or.) and forms a crescentic flap, now extending from the 
second maxilla almost to the labrum. In the next stage (Plate 1, Fig- 
ure 5) the fold is conspicuous ; in lateral aspect (Plate 3, Figure 20) its 
ventral margin is well rounded and conforms posteriorly to the con- 
tiguous anterior surface of the front leg ; the mandibular and maxillary 
fundaments still project slightly below the fold. In ventral aspect (Plate 
3, Figure 21) of the same individual, the fold is seen to be of nearly 
uniform width except anteriorly and posteriorly, where it is expanded 
against the labrum and second maxille respectively. Transections of 
the germ band (Plate 4, Figure 23), when compared with similar sec- 
tions at Stage 3 (Plate 3, Figure 16), show the folds to have exceeded 


136 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


the mandibles in rate of downward growth, and the lateral surface of 
the mandible to be concave, in conformity with the swollen distal region 
of the mouth-fold. 

In Stages 6 and 7 (Plate 1, Figure 6; Plate 2, Figure 7) the folds in- 
volve the labrum and second maxille (Plate 4, Figure 24; Plate 5, Figure 
30, pli. or.), covering the mandibles and first maxillee laterally, and form- 
ing the genze, or sides of the face. As seen in Stage 7 (Plate 5, Figure 
30), each oral fold connects one side of the clypeo-labral fold with the 
labial evagination of the same side. There are no sutures, however, to 
indicate the union of the genz dorsally with the clypeus and ventrally 
with the second maxilla, for the oral evagination, in its backward and 
forward extension, has at length involved the labial and clypeal folds, 
respectively, in such a way that all three folds become one and enclose 
a single common cavity. The anterior margin of the mouth-fold is still 
distinguishable, however, as late as Stages 7 and 8 (Plate 4, Figure 24, 
pli. or.) ; the mesal surfaces of the labial fundaments have not united 
anteriorly (Plate 5, Figure 29); the labrum is free from the fold (Figure 
30) and remains so. The mouth is definitely bounded, but still open 
(Figures 30, 34) ; its closure occurs, however, before the egg hatches. 
The folds — clypeo-labral, oral, and labial — have been converging con- 
comitantly with their elongation, and continue to elongate and converge 
until they meet to form a buccal cone, which completely encloses the 
inner mouth-parts. After hatching, there is, for reasons just given, no 
demarcation of the mouth-fold ; it can simply be said that the region 
designated as pl. or. in Figure 40 (Plate 6) is the anterior part of that 
fold. Also in Orchesella the corresponding region, under which project 
the palpi (Folsom, ’99, Plate 2, Figure 9), doubtless originates as in 
Anurida, but the clypeus is not confluent with the folds. 

Strictly speaking, then, the mandibles and maxille are not “‘ retracted,” 
as is usually stated ; but they are overgrown by the gene. 

Hansen (’93, p. 208) wrote concerning Campodea, Japyx, and Collem- 
bola, ‘die Mandibeln und Maxillen, mit Ausnahme der Spitzen, ‘im 
Kopfe liegen.’ Dieses ist dadurch entstanden, dass sich die Haut hinter 
ihrer Einlenkung wie eine Duplicatur, welche Gewebe enthalt, vorwarts 
und um sie herum gefaltet hat, und die Rander dieser Duplicatur sind 
auf der Unterseite des Kopfes mit dem Seitenriindern des Labiums 
festgewachsen, so dass dieses fast seiner ganzen Linge nach mit der 
Seitenwand des Kopfes verbunden ist.” These facts he ascertained by 
laborious dissections of the finished parts. 

Packard (71, p. 21) simply mentions that “ the cephalic plates, which 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 137 


fold back upon the head, forming the main expansion of the insectean 
head is [are] apparently the tergum of the antennary segment,’ — a 
statement unsubstantiated by later and more extensive studies. 

The only account of the formation of the mouth-folds of Collembola is 
by Miss Claypole, who also studied Anurida maritima, giving her results 
briefly in 1896 and finally in 1898. The following extracts from her 
valuable paper (98, pp. 264-266) summarize her observations and 
conclusions: “On each side of these [three pairs of mouth-parts, as in 
my Stage 3] has appeared a ridge that passes backward along the embryo, 
the two folds enclosing the mandibles and maxillz. These folds start 
from just the region where the small intercalary appendages were seen 
earlier, but which have now disappeared. Figures 43, 46, and 47 show 
the process by which this change takes place, and leave no doubt that 
the folds, as they finally appear, are a development from the intercalary 
appendages. . . . The labrum in front and these lateral. folds make 
together a three-sided box in which the mouth-parts, two mandibles, and 
four maxille are sheltered. . . . The second pair of maxille has been 
modified to form the back of this pouch.” The author (pp. 265-266), 
after homologizing the neuromeres of Orthoptera and Crustacea, draws 
the important conclusion that the mouth-folds of Anurida “ including 
without doubt its allied forms,” are “clearly homologous with the second 
antennee ” of Crustacea. 

I quite disagree with this author as to the origin, and consequently 
the homology, of the mouth-folds. A priori arguments are here super- 
fluous, as the question is one of fact. As I have shown, the folds begin 
on, or very near, the mandibular segment, but always outside the paired 
fundaments of the mouth-parts, and never at the premandibular append- 
ages. The folds eventually and necessarily involve the intercalary region 
on progressing towards the labrum, although previously their early indi- 
cated continuity with the second maxille (Plate 2, Figure 10) is estab- 
lished. Conceptions as to the development of the fold are of course but 
inferences from facts observed in certain stages. The most apparent 
inference from the figures cited by Miss Claypole as leaving no doubt 
about the accuracy of her conclusion is certainly the one she has drawn ; 
but from the same figures and from her preparations — which Miss 
Claypole has most kindly lent me— may also be drawn the less ap- 
parent, though I believe correct, inference that the folds begin between 
the interealary and second maxillary regions and grow towards both of 
them. I have found stages intermediate between those shown by Miss 
Claypole in Figures 46 and 47, which convince me that this is the 


138 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 


case. Consequently the mouth-folds cannot represent the Crustacean 
second antenne. My own views as to the homology of the mouth-folds, 
already implied by my use of the term ‘genx,’ will presently be 
supported. 

Hansen’s recognition of the similarity between Campodea, Japyx, and 
Collembola is sustained by embryology. In Campodea, Uzel (’98, p. 33) 
‘describes and figures a “ Chitinstrang . . ., welcher sich von der Vorder- 
randmitte der zweiten Maxille um die Aussenseite des ersten Maxille 
und der Mandibel herum zu den auf den Intercalarsegmente gelegenen 
Hockern zieht.” His Figures 38 and 79 show the Chitinstrang at a 
rather advanced stage of development, corresponding with the condition 
in my Figure 17; unfortunately he gives neither its origin nor its earlier 
development. The later development, as evidenced diagrammatically by 
his Figures 80-84, agrees with that of Anurida in the gradual approxi- 
mation of the lateral ridges, and especially in the completion of the 
buccal boundary by the same method’ of confluence. Uzel does not 
attempt to explain the homology of the Chitinstrang. 

In Lepisma and Machilis the mouth-parts are ectognathous,.as in 
Orthoptera. In Lepisma there is no trace of a lateral mouth-fold, but 
in Machilis I have found a distinct, flat, lateral lobe sheltering the base 
of each mandible, and the lobe is probably homologous with the Collem- 
bolan mouth-fold. 

In Pterygota the gen, often not demarcated as distinct sclerites, 
represent the lateral regions of the germ band — as they do in Campodea 
and Collembola. In these Apterygota the same areas have simply in- 
creased as folds, but the folds are none the less homologous with the 
pleural regions of other insects, and in Collembola are reasonably to be 
regarded as the pleural portions of the premandibular, mandibular, and 
both maxillary segments. In many Pterygote insects, especially in 
Orthoptera, the gene overlap the bases of the jaws; for example, in 
Caloptenus, in which the gena is produced as a small but distinct flat 
fold over the base of the mandible. 

Little is known about the development of the sides of the head in 
Myriopoda, but in Peripatus it is interesting to find distinct lateral 
mouth-folds (Sedgwick, ’88, Plate IT., Figure 36) quite analogous, to say 
the least, with those of Collembola. 

Concerning the completion of the skull, little remains to be said. At 
Stage 7 a constriction encircling the blastoderm separates the head from 
the thorax. The head is typically a hollow cylinder, or cone, and so is 
the body. The body cylinder consists of a definite number of successive 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 139 


rings, in each of which, in the more specialized insects, tergum, pleura, 
and sternum are present. 

In the head region of the Collembola, however, segmentation occurs 
only on the ventral side of the germ band. The entire gular region is 
labial in origin, and there is reason for regarding the clypeus as the 
tergite of the ocular segment. The mouth-folds are undoubtedly ex- 
panded pleura. Aside from these, however, it is idle to speculate about 
the location of other sclerites which are differentiated in more spe- 
cialized insects. Here, in the absence of such differentiation, it may be 
be said that the head-cylinder represents seven ideal rings, which dorsally 
and laterally are in no way demarcated from each other. Admitting 
that the procephalic lobes do extend backward and encroach upon other 
segments, the lobes may not be regarded as the tergites or pleurites of 
those segments, for they are simply thickened blastoderm, and increase 
in area in proportion as the blastoderm thickens ; but the convenience 
of applying a single term, “ procephalic lobe,” to either of these thicken- 
ings should not blind us to the fact that the lobe eventually represents 
the blastoderm of more than one segment. 

In the finished head (Plate 5, Figure 33) are certain elevated dorsal 
areas which, however, are not sclerites bounded by sutures, and are not 
clearly to be homologized with sclerites of other hexapod orders. The 
elevations referred to are directly correlated with underlying glands and 
muscles. 

The sides of the face in Apterygota, then, are homologous with the 
gene of Pterygota. In all insects the skull represents seven somites, 
but the cephalic sclerites of Pterygota, excepting labrum, clypeus, and 
labial sclerites, are not differentiated in the Apterygota. 


Tentorium. 


The tentorium of Anurida is essentially like that of Orchesella (Folsom, 
’99), consisting of a chitinous plate parallel with the frontal plane (Plate 
8, Figure 51, tvt.), from which diverge two pairs of chitinous arms (Plate 
6, Figure 35) extending to the skull: a dorsal pair (6r. d.) and a poste- 
rior pair (67. p.) embracing respectively the supra- and infra-cesophageal 
ganglion. <A third, or anterior, pair was found in Orchesella, but not in 
Anurida. 

Regarding the development of the tentorium in insects, most diverse 
opinions are held. After considerable study, I have come to the con- 


140 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


clusion that the tentorium of Anurida is derived from proliferated ecto- 
dermal cells which are in no way, except in position, distinguishable 
from young ganglion cells. 

In Anurida, as in Orthoptera (Wheeler, ’93, Heymons, ’95°) and 
Lepisma (Heymons, 97°), the ventral cords consist of dorso-ventral 
rows of cells, which arise by proliferation from the outer ectoderm, 
Although it has seldom been supposed that these cells became other 
than ganglionic in function, it may be assumed, in view of their origin, 
that ail of them are potentially chitin-forming cells, and it seems prob- 
able that some of them actually do form the chitinous tentorium. 

An oblique section of Stage 8, cut at a fortunate angle for studying 
the relation of tentorium to cells, gave the appearance represented in 
Figure 35. Contiguous to practically all parts of the tentorium, in this 
section, are cells the nuclei of which do not differ in appearance from 
nuclei of undoubted ganglion cells. On all sides of the tentorium such 
cells abound and closely embrace it ; an especially large mass of these 
cells occurs immediately under the frontal plate, in which, moreover, 
several cells always become enclosed and appear to be functional in the 
adult. I found no evidence which could be interpreted as indicating 
any other way of formation. 

Von Stummer-Traunfels (91) appears to have overlooked the ten- 
torium of Apterygota, for he mentions the “Stiitzapparate” only, by 
which he evidently means the structures I call ‘lingual stalks.” 

As regards the Thysanura, Meinert (’65, Tab. XIV. Figur 5, 6) men- 
tions in Japyx and Campodea a median chitinous plate, from which the 
mandibular adductors take their origin,.which is undoubtedly the tento- 
rium. Grassi (86°) also alludes to it in Japyx. 

In Machilis the lingual stalks, important in Collembola, become rudi- 
mentary ; and most of the mandibular and maxillary muscles become 
attached to the tentorium ; but they are fewer than in Collembola. The 
tentorium is thus described by Oudemans (’88, p. 186): ‘ Die vor- 
deren [Stiitzplatten] kommen von den Seiten des Clypeus, gleich ober- 
halb der Mahlhohle, wie dieses im Durchschnitt abgebildet ist in Figur 
32. Links und rechts geht dort die Chitinhaut des Clypeus tiber in eine 
Platte. Die beiden Platten niihern sich nach hinten, indem sie fortwih- 
rend breiter werden. In der Mitte des Kopfes kommen sie zusammen, 
sind da jedoch nicht verschmolzen, sondern nur stark durch Bindegewebe 
verbunden, Figur 19 Lt. Hinter dieser Verbindungsstelle weichen die 
Platten wieder auseinander, werden schmiiler und gehen, links und 
rechts vom (Hsophagus, nach oben. Zuletzt geht jede tiber in einen 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 141 


diimnen Chitinstab, welcher oben im Kopfe, hinter den Augen, endet 
und da am Chitin des Kopfes festsitzt.”’ 

Thus, the tentorium of Machilis is constructed upon the same plan as 
that of Anurida, although the median plate is halved longitudinally. 
The dorsal and posterior arms in Anurida are clearly represented in 
Machilis, and the latter pair tends to become reduced in size, — an 
approach to the Orthopteran condition. 

The tentorium in Orthoptera is readily comparable with that of 
Machilis. In Periplaneta, according to Miall and Denny (’86, p. 39), 
“Tn front it gives off two long crura, or props, which pass to the gin- 
glymus, and are reflected thence upon the inner surface of the clypeus, 
ascending as high as the antennary socket, round which they form a 
kind of rim. Each crus is twisted, so that the front surface becomes 
first internal and then posterior as it passes towards the clypeus. The 
form of the tentorium is in other respects readily understood from the 
figure (Figure 17). Its lower surface is strengthened by a median keel 
which gives attachment to muscles. The esophagus passes upwards 
between the anterior crura, the long flexor of the mandible lies on each 
side of the central plate; the supracesophageal ganglion rests on the 
plate above, and the subcesophageal ganglion lies below it, the nerve- 
cords which unite the two passing through the circular aperture. <A 
similar internal chitinous skeleton occurs in the heads of other Orthop- 
tera, as well as in Neuroptera and Lepidoptera.” 

In Anabrus (Packard, ’98, p. 49, Figure 33) the tentorium is essen- 
tially the same, with a central plate, and paired dorsal and posterior 
arms. The only important differences between Orthoptera and Collem- 
bola in respect to the tentorium are (1) that the cesophageal commissures 
pass through it in the former group instead of around it; (2) that in 
Orthoptera the posterior arms are reduced in length, and (3) that the 
tentorium becomes .more stoutly chitinized. On the other hand, the 
tentorium of Orthoptera, in its general form and topographical relations, 
agrees closely with the same structure in Collembola and Thysanura. 

Palmén (’77) derived the tentorium from a pair of cephalic trachez in 
Ephemera, but upon unsatisfactory grounds. In Collembola trachez 
are absent ; moreover, as Packard (’98, p. 50) notes, ‘the apodemes of 
the thoracic region are evidently not modified tracheze, since the stigmata 
and trachez are present.” 

The views of Carriére (90) and Cholodkowsky (91), agreeing with 
the opinion of Palmén, have been controverted by Heymons (’95°, 
pp. 50-51). 


142 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


Wheeler (’89, p. 568) finds that five pairs of ectodermal invaginations 
form the tentorium of the larval head of Doryphora. ‘These invagina- 
tions grow inwards as slender tubes, which anastomose in some places. 
Their lumina are ultimately filled with chitin.” Wheeler offers his 
observations in support of Palmén’s theory, but they are not at all 
inharmonious with the scanty observations I have made upon Anurida. 

Heymons (’95", pp. 50-51), describing Forficula, agrees with Wheeler, 
except that he finds only two pairs of fundaments for the tentorium, and 
says (p.51): ‘Ich habe mich indessen davon tiberzeugt, dass auch bei 
Gryllus und Periplaneta die zahl der Tentoriumanlagen keine gréssere 
ist, sondern, wie Heider (89) dies bei Hydrophilus beschrieb, und ich es 
bei Forficula fand, nur vier betrigt. Der oben geschilderte Entwicke- 
lungsmodus des Tentoriums diirfte daher wohl als der typische anzusehen 
sein.” E 

In Anurida I was unable to find any distinct ectodermal invaginations 
which might form the arms of the tentorium, but am not prepared to say 
that none exist, because the subject is one of great difficulty. The arms 
must be studied in oblique sections, and it is almost impossible to dis- 
tinguish them from fundaments of muscles until they are nearly com- 
pleted. The finished tentorium of Collembola, however, is undoubtedly 
homologous with that of Thysanura, and almost as clearly with the ten- 
torium of Orthoptera. 


Segmentation of the Head. 


The elucidation of the primitive segments in Arthropods is a most 
interesting and difficult morphological problem. The rule of Savigny, 
— emphasized by Huxley and others, — that Arthropods consist funda- 
mentally of successive rings, each of which may bear but one pair of 
primary appendages, although now undoubted, has never been thoroughly 
substantiated when applied to the Hexapod head. After vears of argu- 
ment, morphologists still disagree as to the number of somites composing 
the highly differentiated heads of insects. Kolbe (’90, p. 135) recognizes 
five, as follows :— 

1. Ursegment : Fihler, Augen, Oberlippe ; 

2. Ursegment : Oberkiefer oder Mandibeln (1. Kiefernpaar) ; 

3. Ursegment: Unterkiefer oder Maxillen (2. Kiefernpaar) ; 

4, Ursegment : Zunge oder Innenlippe (3. Kiefernpaar, verwachsen) ; 

5. Ursegment: Unterlippe (4. Kiefernpaar, verwachsen). 

Sharp (95, p. 87) says, “ Morphologists are not yet agreed as to their 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA 143 


number, some thinking this is three, while others place it as high as 
seven ; three or four being, perhaps, the figures at present most in favor, 
though Viallanes, who has recently discussed the subject, considers six, 
the number suggested by Huxley, as the most probable. Cholodkowsky 
is of a similar opinion.” 

Packard (’98, p. 54) gives six : — 


Preces oR REGIONS 


NAME OR SEGMENT. OF THE HEAD-CAPSULE. 


APPENDAGES, ETC. 


. Ocellar 
(Protocerebral). 


Epicranium, ante- 
rior region with 
the clypeus, la- 
brum, and _ epi- 
pharynx. 


Compound and sim- 
ple eyes (ocelli). 


Pre-oral 
in early embryo. 


. Antennal Epicranium, includ-} Antenne. 


Post-oral 


(Deutocerebral). 


. Premandibular, or 


Intercalary 
( Tritocerebral). 


. Mandibular. 


ing the antennal 
sockets. 


Wanting in post- 
embryonic life, ex- 


cept in Campodea. 


Epicranium behind 


theantenne, gene. 


Premandibular 
appendages 
(in Campodea). 


Mandibles. 


in early embryo. ; ; 
Epicranium, hinder | First maxille. 


edge? tentorium. 


5, First Maxillary. 


Second maxilla, or 
labium.  Post- 
gula, gula, sub- 
mentuin, mentum, 
hypophary nx (lin- 
gua, ligula), para- 
gloss, spinneret. 


. Second Maxillary, 
or labial. 


Occiput. 


Upon anatomical grounds, different observers have recognized from 
one to seven head segments. As mentioned by Packard (98, p. 50), 
Burmeister found but two; Carus and Audouin three ; MacLeay, New- 
Huxley (’78, p. 343) 
said: “It is hardly open to doubt that the mandibles, the maxille, and 
the labium answer to the mandibles and the two pairs of maxille of the 
crustacean mouth. In this case, one pair of antennary organs found in 
the latter is wanting in insects, as in other air-breathing Arthropods, 
and the existence of the corresponding somite cannot be proved. But if 
it be supposed to be present, though without any appendage, and if the 


man, and Newport four ; Straus-Durckheim seven. 


144 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


eyes be taken to represent the appendages of another somite, the insect- 
head will contain six somites.” ... 

Huxley’s conclusions were the most satisfactory that could be derived 
from a study of the completed organs alone, and reduced the problem to 
these questions: Do the eyes represent a somite? Is another antennal 
segment represented in insects? Do the labrum and hypopharynx repre- 
sent distinct segments ? 

Authors began to realize the impossibility of settling the problem upon 
purely anatomical data, and attacked it from the embryological side. 

Packard (71, p. 21) concluded, “ Accordingly, we seem forced to the 
belief that the head of the hexapodous insects consists of but four seg- 
ments, 2. e. the second maxillary, first maxillary, and mandibular seg- 
ments, situated behind the mouth opening, and the antennary, or first 
and pre-oral segment, situated in front of the mouth. . . . The clypeus 
and labrum are apparently differentiated from the cephalic lobes, and 
thus seem to form a portion, or fold, of the antennary segment.” Graber 
(779) reached the same conclusion. 

Viallanes, after carefully studying the development of the nervous 
system in Insects and decapod Crustacea, wrote the most important 
contribution upon the subject that has yet been published, and gave his 
results as follows (87, pp. 108-109) :— 


“1. Le cerveau des Insectes, comme le cerveau des Crustacés décapodes, est 
formé de trois segments : j’appelle le premier protoccrebron (cerveau du pre- 
mier zoonite) ; le deuxiéme, deutocerébron (cerveau du deuzitme zoonite) ; le 
troisitme, tritocérébron (cerveau du troisieme zoonite). 

“2. Nous retrouvons, dans le protocérébron de l’Insecte, toutes les parties 
constitutives du protocérébron du Crustacé. Dans cette premiere région céré- 
brale, la seule différence qui s’observe entre les deux types est la suivante : chez 
V'Insecte les deux lobes protocérébraux viennent se souder sur la ligne médiane 
et se mettre ainsi en contact avec le protocérébron moyen. Chez le Crustacé, 
au contraire, les lobes protocérébraux sont trés écartés de la ligne médiane et 
logés dans les pédoncules oculiféres. Le rapprochement qui, chez 1’Insecte, 
s’effectue entre les lobes protocérébraux, entraine la disparition, ou pour mieux 
dire le raccourcissement extréme du tractus nerveux connu chez les Crustacés 
sous le nom de nerf optique. 

“3. La deutocérébron, qui a une structure extrémement caractéristique, se 
retrouve chez |’Insecte et chez le Crustacé avec les mémes caractéres et les 
mémes connexions. I] en résulte que le nerf antennaire de |’Insecte est 
Vhomologue du nerf de Vantennule du Crustacé. 

“4. Chez le Crustacé le tritocérébron se compose des deux lobes antennaires 
et des deux ganglions csophagiens (improprement appelés mandibulaires) et 
d’une commissure sous-cesophagienne (la commissure transverse de l’anneaw 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 145 


cesophagien) qui réunit ces derniers. Le lobe antennaire donne naissance au 
nerf de l’antenne externe, le ganglion cesophagien & la racine du premier gan- 
glion visceral impair (ganglion stomatogastrique) et au nerf du labre. 

“ Chez l’Insecte, le tritocérébron subit une importante réduction, les lobes 
et les nerfs antennaires disparaissent, mais les représentants des ganglions 
cesophagiens (que j’ai décrits sous le nom des lobes tritocérébraux) subsistent 
dans leur intégrité. Comme chez le Crustacé, ils donnent naissance & la racine 
du premier ganglion viscéral impair (ganglion frontal) et au nerf du labre ; 
comme chez les Crustacés, ils sont unis ’un & Vautre par une commissure 
sous-eesophagienne (commissure transverse de l’anneau cesophagien). Ainsi : 

“Te nerf de Vantenne externe du Crustacé n’est pas représenté chez 
1’Insecte. 

“Le nerf du labre de VInsecte est Vhomologue du nerf du labre du 
Crustacé.” 


After a lengthy discussion of the segmentation of the head, Viallanes 
concludes (’87, pp. 117-118) : — ‘ 


“1, La téte de l’Insecte est formée par six zoonites, trois sont pré-buccaux et 
trois post-buccaux. 

“2. Le premier zoonite porte les yeux composés et les ocelles. Le deuxieme 
les antennes. Le troisiéme, qui est dépourvu d’ appendices, porte le labre, piece 
qui, pas plus chez les Insectes que chez les Crustacés, ne peut étre considérée 
comme le résultat de la soudure de deux appendices. 

“3. Le quatriéme zoonite porte les mandibules, le cinquiéme les machoires, 
le sixiéme la lévre inférieure.” 


Wheeler (’93), Heymons (’95*), and others have confirmed these 
conclusions. 

Heymons (’95%, p. 36), in a valuable paper on the segmentation of the 
insect-body, says, “ Der Kopf besteht aus sechs Korperabschnitten : dem 
Oralstiick, Antennensegment, Vorkiefersegment, und drei Kieferseg- 
menten.” 

Rudimentary intercalary appendages have been found in Anurida 
(Wheeler, ’93) and Campodea (Uzel, 97°). Claypole (98) and Uzel (’98) 
have homologized them with the second antennz of Crustacea, 

Six somites are the most that have been admitted upon embryological 
grounds, but I am convinced that there are more than six. 

Hansen (’93) suggested that the so-called ‘ paraglossz ” [superlinguz] 
of Machilis were homologous with the Crustacean first maxille, and my 
observations upon the development of the superlingue support his view. 
The superlingne originate independently as a pair of simple papillae — 
like the mandibles and maxillee — intermediate between the mandibles 
and the “ first maxille,” and represent a distinct, though reduced, seg- 


146 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


ment, because provided with a ganglion. More conclusive proof could 
hardly be expected. 

The insect-head, then, is composed of seven somites, which are homolo- 
gous with the first seven of decapod Crustacea. 

If the conclusions I have drawn in this paper are valid, certain radical 
changes become necessary in the commonly accepted ideas of homology 
among the great classes of Arthropods. These changes I submit in the 


following table : — 


TABLE OF EQUIVALENT SOMITES IN THE HEAD OF ARTHROPODA. 


Segment| Arachnida | Chilopoda Diplopoda Crustacea Hexapoda 


Compound 
eyes and 
ocelli 


Compound 
eyes and 
ocelli 


First 
antenne 


Embryonic 
preantenne. 


Antenne 


Second 
antenne 


Intercalary 
appendages 


Antenne Antenne 


Chelicerz 


Pedipalpi 


Mandibles 


First 
maxille 


Second 


Mandibles 


Mandibles 


First 
maxille 


Second 


Mandibles 


Superlingue 


Maxille 


First legs Gnathochilarium 


maxille maxille 


First Labium 


Second legs Maxillipedes 
maxillipedes 


Summary. 


The protocerebrum of Apterygota agrees with that of other insects 
in development and structure. The ocular segments of Hexapoda and 
decapod Crustacea, as well as the compound eyes of the two groups, are 
homologous. 

The labrum and clypeus of insects develop from a single median 
evagination between the procephalic lobes, and do not represent a pair 
of appendages. The labrum of Apterygota is homologous with that of 
other insects, as well as that of Symphyla, Diplopoda, Chilopoda, and 
the higher Crustacea. 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA., 147 


The antenne of Apterygota evaginate from the posterior boundaries 
of the procephalic lobes, and therefore agree with those of Pterygota in 
this respect. In both groups the antenne are at first post-oral and sub- 
sequently pre-oral in position. 

The deutocerebrum of insects is homologous with that of Crustacea, 
and the antenne of Hexapoda are equivalent to the antennules of 
Crustacea and the embryonic preeantennee of Chilopoda. 

Premandibular, or intercalary, appendages exist in the embryo of 
Anurida, and appear to be represented even in the adults of several 
Apterygote genera. The tritocerebrum of Apterygota is homologous 
with that of Orthoptera and decapod Crustacea, and the rudimentary 
premandibular appendages of Collembola and Thysanura represent the 
second antennz of decapod Crustacea and probably the antenn of 
Diplopoda and Chilopoda. A distinct primitive ganglion occurs in the 
intercalary segment of Anurida, therefore the segment must be regarded 
as one of the primary head-segments. 

The mandibles of Apterygota develop from a pair of simple papille, 
the bases of which become oblique. No trace of lobation occurs except 
in Campodea. The mandibles of Collembola and Thysanura are homo- 
dynamous with the maxille and homologous with the mandibles of 
Pterygota, Scolopendrella, Crustacea, and probably Diplopoda and 
Chilopoda. 

The “hypopharynx” in Apterygota is a compound structure consist- 
ing of two dorsal “superlingue,” —as I have called them, — which 
develop from a pair of papillee between the mandibular and first maxil- 
lary segments, and also a ventral lingua, which originates independently 
as a median unpaired evagination on the first maxillary segment. The 
two chitinous “lingual stalks,” which are most highly developed among 
Apterygota, arise in superficial grooves of the ectoderm. The hypo- 
pharynx of Apterygota is undoubtedly homologous with that of Ptery- 
gota; although, in the latter group, the lingua and superlinguze become 
united together and the lingual stalks become rudimentary. In Anurida 
a distinct neuromere exists for the “ superlingue ;” therefore it is neces- 
sary to recognize the superlingual segment as equivalent in morphologi- 
cal value to the other primary somites. The superlingue are homologous 
with the first maxillze of Malacostraca and Chilopoda and are anatomi- 
cally represented in the labial plate of Diplopoda. In order to avoid 
confusion, the terms “ paraglosse ” and “ligula” should not be applied 
to the constituents of the hypopharynx, but are better restricted to the 
labium of insects. The lingua of Hexapoda is equivalent to the Crusta- 


148 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


cean hypopharynx, and possibly also to the median component of the 
Diplopod gnathochilarium. 

The first maxillze in Collembola and Thysanura develop essentially 
as in Orthoptera and may be homologized part for part with the maxille 
of generalized Pterygota. In Anurida a palpus appears in the embryo, 
but is resorbed before hatching, indicating the derivation of this genus 
from a form in which the first maxillary palpi were functional, as they 
are at present in Orchesella, Tomocerus, and other Collembolan genera. 
The first maxille of Campodea are clearly to be homologized with the 
first of Scolopendrella, the second of Chilopoda, and less clearly with the 
lateral portions of the Diplopod gnathochilarium. The first maxille of 
insects pass through a biramons condition, as in Crustacea, and the 
sclerites of these organs appear to be homologous in the two groups; 
the first maxilla of Hexapoda, however, are equivalent to the second 
maxillte of Malacostraca. 

The labium in Anurida develops from a pair of papillee, from which 
the entire gular region is derived. A palpus appears, but is soon re- 
sorbed, and no galeal and lacinial lobes are differentiated. Upon the 
whole, the labium among Apterygota is homologous with the same 
structure of Pterygota, although fewer sclerites are formed in the 
former group. The labium in insects, homodynamous with the man- 
dibles and first maxilla, agrees in detail with the first maxillipedes of 
decapod Crustacea. The labium of Campodea is homologous with the 
“second maxille” of Scolopendrella and the maxillipeds of Chilopoda, 
and is represented in the gnathochilarinm of Diplopoda. 

The sides of the face in Anurida develop from two lateral evaginations 
of the germ band near the mandibular segment, which eventually involve 
the labral and labial fundaments and complete the buccal cone. The 
mouth-folds of Collembola, Campodea, and Japyx are strictly homologous 
with the gene of Pterygota. The dorsal region of the skull in Anurida 
does not differentiate into sclerites which may be compared with those 
of Pterygote insects. 

The tentorium is inferred to develop from cells which have been pro- 
liferated from the ectoderm. 

The evidence convinces me that there are just seven somites in the 
head of Anurida, and that probably the same is true for all Hexapoda. 
The cephalic somites are successively: ocular, antennal, intercalary, 
mandibular, superlingual, maxillary, and iabial. As I have found — 
embryonic ganglia for the intercalary and superlingual segments, there 
are seven cephalic ganglia, one for each somite. Moreover, excepting 


FOLSOM: “MOUTH-PARTS OF ANURIDA MARITIMA. 149 


the ocular segment, every somite is represented by a pair of append- 
ages. I find no evidence whatever for more than seven primitive 
cephalic segments, and believe that my observations have assisted 
to settle the long-disputed question of the segmentation of the 
head. : 

Since the time of Fabricius, the mouth-parts of insects have been of 
primary importance for the systematist. While insisting that a logical 
classification must recognize all anatomical structures, it must be ad- 
mitted that the mouth-parts are of fundamental systematic value on 
account of the range of their differentiation. 

Without discussing at length the phylogeny of insects, I may briefly 
give the bearing of these studies upon the subject, remarking that my 
conclusions are in entire accord with approved views upon the origin 
of insects. 

The Collembola are strikingly like Campodea and Japyx in structure, 
their peculiar entognathous characteristic separating these three groups 
from all other insects. The Collembola as a group are somewhat more 
specialized than the Thysanura in general structure. The Smynthuride, 
with their globular bodies, vertical heads, and well-developed furcule 
and ventral tubes, represent one extreme of differentiation — compara- 
tively high. The Aphoruride, including Anurida, with vermiform 
bodies, subequal segments, horizontal heads, no furcula, etc., are much 
more generalized, and probably degenerate forms. Anurida, for ex- 
ample, has both pairs of maxillary palpi, as well as rudimentary ab- 
dominal appendages and the fundaments of a furcula in the embryo, 
but in the embryo only. Therefore the ancestral Collembolan was 
probably intermediate between Smynthuride and Aphoruride, and is 
most nearly represented by members of the family Poduride. The 
resemblance in the mouth-parts leads us to suppose that the primitive 
Collembolan descended from the stem form of Campodea and not far 
below Campodea itself. 

The affinities of Campodea, which is slightly more primitive than 
Japyx, are in two.directions: towards Machilis and Lepisma on the one 
hand, and towards Scolopendrella on the other. In the first two genera 
the mouth-parts are clearly derivable from the Campodean type, and 
link Campodea with Orthoptera. In regard to Scolopendrella, it was 
long uncertain whether it should be placed among Thysanura or 
Myriopoda, on account of its strong affinities for both. Most authors 
have followed Grassi and placed it in the latter group, always admitting 


its insectean features. In the month-parts, Scolopendrella approaches 
VOL. XXXVI. — NO. 5 5 


150 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


Campodea rather than Diplopoda, but is unquestionably nearer Diplo- 
poda than it is to Chilopoda. 

The gnathochilarium of Diplopoda may be homologized with the 
appendages of three hexapod somites, but only two embryonic segments 
have as yet been found ; and the subject needs further investigation. 

The mouth-parts of Chilopoda may be homologized with those of 
insects in only the broadest way, the correspondences being principally 
those of position. 

Between decapod Crustacea and Apterygota there are decided mor- 
phological resemblances. The seven cephalic somites which I have 
found in the latter group I have homologized in detail with the anterior 
seven of the former, and pointed out that most of the homologous ap- 
pendages function alike in the two groups. These homologies, however, 
simply indicate a partial parallelism in development; for in most re- 
spects Crustacea and Hexapoda are very divergent classes. 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. * 151 


BLE LT OG RAP EY, 


Ayers, H. 
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Carriére, J. 
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96. The Appendages of an Insect Embryo. Can. Entom., Vol. 28, p. 289. 
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Dugés, A. 
32. Recherches sur les caractéres zoologiques du genre Pulex, et sur la 


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pp. 145-165, Pl. 4. 


152 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


Folsom, J. W. 
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Orchesella cincta L. Bull. Mus. Comp. Zodl., Vol. 35, No. 2, pp. = 
4 pl. 
Grassi, B. 

"85. Studi sugli Ariropodi. Intorno allo sviluppo delle api nell’ uovo. Ati 

Acead. Gioen. Sci. Nat. Catania, Ser. 3, T. 18, pp. 145-222, 10 tav. 
Grassi, B. 

"863. I progenitor degli Insettie dei Miriapodi. [Memoria I] Morikese 
delle Scolopendrelle. Mem. Reale Accad. Sci. Torino, Ser. 2; T. 37, 
pp- 593-624, 2 iav. ; 

Grassi, B. 

*86>. I progenitori degli Insetti e dei Miriapodi. [Memoria II] L’Japyx e 
la Campodea. Atti Accad. Gioen. Sci- Nat. Catania, Ser. 3, T. 19, pp. 1— 
83, Tav. 1-4. 

Grassi, B. 

"86e. I progenitori dei Miriapodi e degli Insetti. Memoria III. Contribu- 
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Sci. Nat. Catania, Ser. 3, T. 19, pp. 101-128, 1 tav. 

Hansen, H. J. 
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Tuseciten. Zool. Anz., Jhg- 16, pp. 193-198, 201-219. 
Hansen, H. J. 
"94. On the Structure and Habits of Hemimerus talpoides Walk. Entom. 
Tidsk., Arg. 15, pp- 65-93, Pl. 2, 3. 


Heider, K. 
°89. Die Embryonalentwicklung von Hydrophilus piceus L. 98 pp., 13 Taf. 


Jena. 
Heymons, R. 
*953. Die Segmentirung des Insectenkorpers. Anhang z. d. Abh. Kongl. 
Preuss. Akad. Wiss., Berlin, 39 pp., 1 Taf. 
Heymons, R. 
°950. Die Embryonalentwickelang von Dermapteren und Orthopteren unter 
besonderer Bericksichtizung der Keimblatierbildung. viii, 136 pp., 
12 Taf. wu 33 Fig. Jena. 
Heymons, R. 
°96. Grundzige der Entwickelung und des K6rperbaues von Odonaten und 
Ephemeriden. Anhang z.d. Abh. Kongl. Preuss. Akad. Wiss., Berlin. 
66 pp-, 2 Tai. 
Heymons, R. 
973. Entwicklaungsgeschichtliche Untersuchungen an Lepisma saccharina L. 
Zeiis. £. wiss. Zool., Bd. 62, pp. 583-631, Taf. 29, 30. 3 Fig. 


FOLSOM: MOUTH-PARTS OF ANURIDA MABITIMA. 153 


Heymons, R. 
°97>. Mittheilungen aber die Segmentirang und den Korperban der Myrio- 
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2 Fig. 
Separate, 9 pp-, 2 Fig. 
Hollis, W. A. 
*72. The Homologue of a Mandibular Palp in Certain Insects. Jour. Anat- 
Phys., Vol. 6, pp. 395-397, PL 18. 
Huxley, T. H. 
*78. A Manual of the Anatomy of Inveriebrated Animals. 596 pp., 158 fig. 
New York. 
Kirby, W., and Spence, W. 
728. An Introduction to Entomology. Ed. 5,4 vols. London. 
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89-93. Eimfuhrong in die Kenninis der Insekten. xi, viii, 709 pp-, 324 
Fiz. Berl 
Korotneff, A. 
*85. Die Embryologie der Gryllotalpa. Zeits. f. wiss. Zool., Bd 41, pp. 579- 
604, Taf. 29-31. 
Korschelt, E., und Heider, K. 
*90-93. Lehrbuch der vergleichenden Entwicklungsgeschichte der wirbel- 
losen Thiere. xu, 1509 pp., 899 Fig. Jena. 
Laizel, R. 
*84. Die Mynropoden der Osterreichisch-ungarischen Monarchie. Zweite 
Halfte. xii, 414 pp., 16 Taf. Wien. 
Le Conte, J. L., and Hom, G. H.- 
*83_. Classification of the Coleoptera of North America. Smiths. Miscel. Coll. 
[No.] 507. xxxviil, 567 pp. Washingion. 
Lemoine, V- 
"83. Recherches sur le développement des Podurelles. Assoc. Fr. PAv. 
Sci, lis Session (1882). pp. 483-520. Pl. 14-16. 
Lubbock, J. 
*73. Monograph of the Collembola and Thysanura. Ray Soc. x, 276 pp., 
78 pl. 
Meinert, F. 
*65. Campodez : en familie af Thysanurernes orden. Naturh. Tidsskr. Rek 
3, Bd. 3, pp. 400-440, Tab. 14. 
Translation: Ou the Campodex,a Family of Thysanura. Ann. Mag. 
Nat. Hist., Ser. 3, Vol. 20, pp. 361-378, 3 fig. 1867. 
Meinert, F. 
*83. Caput Scolopendre. The Head of the Scolopendra and its Muscular 
System. 77 pp., 3 tab. Copenhagen. 


154 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


Metschnikoff, E. 
°74. Embryologie der doppeltfiissigen Myriapoden (Chilognatha). Zeits. f. 
wiss. Zool., Bd. 24, pp. 253-283, Taf. 24-27. 


Metschnikoff, E. 
"75. Embryologisches tiber Geophilus. Zeits. f. wiss. Zool., Bd. 25, pp. 313- 
322, Taf. 20, 21. 


Miall, L. C., and Denny, A. 
86. The Structure and Life History of the Cockroach. 224 pp., 125 fig. 
London. 
Muhr, J. 
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Nassonow, N. 
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Nicolet, H. 
42. Recherches pour servir a l’luistoire des Podurelles. Nouv. Mém. Soe. 
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Olfers, E. de. 
62. Annotationes ad Anatomiam Podurarum. Diss. inaug. Berolini. 36 pp. 
4 tab. 


Oudemans, J. T. 


87. Bijdrage totde Kennis der Thysanura und Collembola. 104 pp., 3 pl., 
Amsterdam. 


Oudemans, J. T. 
88. Beitrage zur Kenntniss der Thysanura und Collembola. Bijdr. Dier- 
kunde, Zool. Genootsch., — Natura Artis Magistra — Amsterdam. Aflev. 
16, pp. 147-226, 3 Taf. [Translation of ’87, with brief additions. ] 


Oulganine [W. N_]. 
75. Sur le développement des Podurelles. Arch. Zool. expér., T. 4, pp. 
xxix—xl. [Abstr. by M. de Korotneff. ] 


Oulianine [W. N.]. 
°76. Développement des Podurelles. Arch. Zool. expér., T. 5, pp. Xvil-—xix. 
[ Résumé by the author. ] 


Packard, A. S. 
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Genus Isotoma. Mem. Peabody Acad. Sci., No. 2, 21 pp., 3 pl., 6 fig. 


[Packard, A. S]. 
°83a. The Systematic Position of the Orthoptera in Relation to other Orders 
of Insects. Third Report U.S. Ent. Comm.,, ete. pp. 286-345, [7-12], 

Pl. 23-64. Washington. 


FOLSOM: MOUTH-PAKTS OF ANURIDA MARITIMA. 155 


Packard, A. S. 
°83>. On the Morphology of the Myriopoda. Proc. Am. Phil. Soc., Vol. 21, 


pp. 197-209, 3 fig. 
Packard, A. S. 
°98. A Text-book of Entomology. 729 pp., 654 fig. New York. 
Palmén, J. A. 
"77. Zur Morphologie des Tracheensystems. 149 pp., 2 Taf. Helsingfors. 
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84. The Development of Phryganids, with a Preliminary Note on the De- 
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Rath, O. vom. 
86. Beitrage zur Kenntniss der Chilognathen. Inaug.-Diss.Bonn, 38 pp., 
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Reichenbach, H. 
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91. Vergleichende Untersuchungen tiber die Mundwerkzeuge der Thysanu- 
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"72. Sveriges Podurider. Kongl. Svensk. Vetens. Akad., Handlingar. Stock- 
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97a. Vor aufige Mittheilung iiber die Entwicklung der Thysanuren. Zool. 
Anz., Bd. 20, pp. 125-182. 


156 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


Wizel\ er: z 
97>. Beitrage zur Entwicklungsgeschichte von Campodea staphylinus Westw. 
Zool. Anz., Bd. 20, pp. 232-237. 


Uzel, H. 
98. Studien tiber die Entwicklung der apterygoten Insecten. vi, 58 pp., 
6 Taf., 5 Fig. Berlin. 


Vayssieére, A. 
°82. Recherches sur lorganisation des larves des Ephémérines. Ann. Sci. 
Nat., Sér. 6, Zool., T. 13, 137 pp., pl. 1-11. 


Viallanes, H. 
87. Etudes histologiques et organologiques sur les centres nerveux et les 
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Walter, A. 
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Bd. 18, pp. 751-807, Taf. 23, 24. 


Westwood, J. O. 
°39. An Introduction to the Modern Classification of Insects, etc. Vol. 1, 
xii, 462 pp. London. 


Wheeler, W. M. 
°89. The Embryology of Blatta germanica and Doryphora decemlineata. 
Jour. of Morph., Vol. 3, pp. 291-886, Pl. 15-21, 16 fig. 


Wheeler, W. M. 
°93. A Contribution to Insect Embryology. Jour. of Morph., Vol. 8, pp. 1- 
160, Pl. 1-6, 7 fig. 
W ood-Mason, J. 
°79. Morphological Notes bearing on the Origin of Insects. Trans. Entom. 
Soe. London, 1879, pp. 145-167, 9 fig. 


Woodworth, W. McM. 
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Comp. Zodl., Vol. 25, No. 3, pp. 43-47. 
Zograff, N. 
’83. Marepiaan kb nosHaHiw 9MOpionasbnaro pasButia Geophilus ferrugineus 
L. K. nm Geophilus proximus L. K. Tpyazn a6. mpu sdooror. Myseb 
Mockosckaro Yuusepcntera, Toms 2. Bum. 1. 
Useberia Hunep. O6mecr. Jw6ur. Ecrecr., Aurponos. u 3raorp. Toms 
xliii. Bum. 1. 
[Contributions to the Knowledge of the Embryological Development of 
Geophilus ferrugineus L. K. and Geophilus proximus L., K. Studies Lab. 
Zool. Mus. Moscow Univ., Vol. 2, Pt. 1. 77 pp., 108 fig. ] 


FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 157 


EXPLANATION OF PLATES. 


All figures were drawn with the aid of a camera lucida, from preparations 


add. . 


app. ab.1-3 . 
app. pr’md. 


app. thr, 


Ciee cs 
ate. . 
ba., ba’. 
br. d. 

br. p. 
cav. bue. 
cd. v. 
COUs 
cht. 
clyp. 
coel. . 
cpt. . 
Gest. 
cta. 

d. 

de. 
dep. . 
dew’ceb. 
dil. 

hy Ae 
ec’drm. . 
ga. 

gn. inf’. 


gn. swe. 


Wdrm. . 
i. . 

cls. 
labs e 
lbr. 

Lor Fe 
Ing. 

ln. v. 


of Anurida maritima Guer. 


ABBREVIATIONS. 

Adductor. lvt. 
Abdominal appendages, mb. 

Ist, 2d, 3d. mb. rug. 
Premandibular append- md. . 

ages. ms’drm. 
Thoracic appendages, mu. . 

Ist, 2d, 3d. mx. 
Antenna. mx? . 
Articulation, or hinge. nl. gn. 
Base. ocl. 
Dorsal arm. Oude. 
Posterior arm. @. 
Buccal cavity. 0. pat 
Ventral cord. or. 
Pivot. pd. 
Chitin. pd’. 
Clypeus. phy. 
Coelom (body cavity). pig: 
Head. pli. 
Constrictor. pli. or 
Cuticula. a plp. . 
Dorsal. pr’ceb. 
Teeth. prd. . 
Depressor. prj. 
Deutocerebrum. prt.l 
Dilator. prt. ms. 
Duct. rel. 
Ectoderm. sng. cp’. 
Galea. sta. 
Infra-esophageal gan- stmd. 

glion. stp. 
Supra-cesophageal gan- sul. 

glion. sul. n. 
Hypodermis. swlnq. 
Intima. sut. 
Incisive. sut.m. 
Labium. te. q. 
Labrum. nite ae 
Lacinia. tri’ceb. . 
Lingua. v. 


Linea ventralis. 


yk. 


Elevator. 
Membrane. 
Corrugated membrane. 
Mandible. 
Mesoderm. 
Muscle. 

First maxilla. 
Second maxilla. 
Ganglionic nucleus. 
Ocellus. 

Dorsal organ. 
(CHsophagus. 
Post-antennal organ. 
Mouth. 

Foot. 

Footstalk. 
Pharynx. 
Pigment. 

Fold. 

Mouth fold. 
Palpus. 
Protocerebrum. 
Proctodeum. 
Projection. 
Lateral protrusor. 
Mesal protrusor. 
Retractor. 
Blood corpuscle. 
Stirrup. 
Stomodeum. 
Stipes. 

Trough. 

Neural groove. 
Superlingua. 
Suture. 

Median suture. 
Germ band. 
Tentorium. 
Tritocerebrum. 
Ventral. 

Yolk. 


Foutsom. — Development Anurida, 


PEATE) a: 


Figs. 1-6 represent views of the left side of eggs (embryos) at Stages 1 to 6 respec- 
tively, with the outer egg membrane removed. X 160. 


Prana elk 


B, Meisei, lith, Buston 


ad. 


: xe 
eel?) 


RO L0¢ ¢ Yel 
0G oscan 
SERCO OR OY 


a 


FOLSOM -DEVELOPMENT ANURIDA. 


f sc 
NOG: 


pare tse) Batcnde hen er ames ones hs elit aren 
> 
, 

= 


rT Pally Witte 
Sera —- al \ aaa rie i ay - _ 
ae es ae) oe a ee eee 9 be 
a io ) tap « : 
a Se WiVETess s OTe te s.- 
ie ae eine ae 
“a Te rs ee 7 
7 ry 4% 4 
j 
= _— 
ae 7 
J + 
~ | — 
an 
: oe 
-_ - 


Foutsom. — Development Anurida. 


PLATE 2. 


Fig. 7. View of left side of embryo at Stage 7, with the outer egg membrane 
removed. x 160. 

Fig. 8. Ventral aspect of germ band at Stage 1. X 150. 

Fig. 8a. Ventral aspect of a portion of the germ band at Stage 1 more highly 
magnified. X 480. 

Fig. 9. Left aspect of cephalic region at Stage 5. X 480. 

Fig. 10. Right aspect of cephalic region at Stage 3. X 480. 

Figures 9 and 10 are from the same preparation. 


PLATE 2. 


DEVELOPMENT ANURIDA. 


+ 
- 
eo 


FOLSOM 


Urry iid ‘ 


25-2 
ei Gee) 


ey Oh 


a) 
JOOS omens S000 
9) 


erseeae 


B. Meisel, lith. Beston 


IWF del . 


Fouisom. — Development Anurida 


Bigs bt 
Fig. 12. 
Fig. 18. 
Fig. 14. 
Fig 15. 
Fig. 16. 
Fig. 17. 
Fig. 18. 
Fig. 19. 
Fig. 20. 
Fig. 21. 
Fig. 22, 


PLATE 3. 


Ventral aspect of cephalic region of germ band at Stage 3. 480. 
Ventral aspect of cephalic region of germ band at Stage 4. 480. 
Sagittal section of labrum at Stage 3. X 762. 

Transection of germ band at the labial segment in Stage 3. X 762. 
Transection of germ band at the first maxillary segmentin Stage 3. X 762. 
Transection of germ band at the mandibular segment in Stage 3. X 762. 
Posterior aspect of left first maxilla at Stage 3. x 480. 

Posterior aspect of left second maxilla at Stage 3. X 480. 

Left aspect of germ band at Stage 4. > 480. 

Left aspect of cephalic region at Stage 5. > 480. 

Ventral aspect of cephalic region at Stage 5. » 480. 

Posterior aspect of left first maxilla at Stage 5. X 480. 


The last three figures are from the same preparation. 


Fotsom. — Development Anurida. 


Fig. 23. 


Fig. 24. 


Fig. 25. 
Fig. 26. 
Fig. 27. 
Fig. 28. 


PLATE 4. 


Anterior aspect of a transection of germ band at mandibular segment in 
Stage 7. The section being thick shows both mandibles and, behind 
them, the superlinguz. X 762. 

Left aspect of embryonic head, represented as if transparent, at Stage 7. 
x 480. 

Ventral aspect of lingua and first maxilla at Stage 7. 480. 

Dorsal aspect of head of right maxilla at Stage 8. X 762. 

Dorsal aspect of lingua and superlingue at Stage 7. X 762. 

Paramedian section to show the primitive cephalic ganglia at Stage 5. X 
762. 


PLATE 4. 


FoLSOM-DEVELOPMENT ANURIDA. 


Car 


s 
& 
va S 
Taey ROCKS, RS 
‘5 aaa Oeeeee  S 
Rp RAS g tava orto) 
19! e) nO7S i x) 4 i 
eke a CD, oy) 
sp conelelelen ae ater 
FERS SO UAE) 


B. Meisel, lith, Boston 


JWF. del 


Foisom. — Development Anurida. 


PLATE 5. 


. Ventral aspect of head, represented as if transparent, at Stage 7. 480. 
. Anterior aspect of mouth-parts at Stage 7. From the same preparation 


as Figures 24 and 29. »X 480. 


. Paramedian section of head at Stage 7. X 480. 

. Ventral aspect of left maxilla at Stage 7. X 762. 
3. Dorsal aspect of adult head.  X 45. z 
. Anterior aspect of mouth at Stage 8. x 480. 


PEATE, (5% 


FoLsOM-DEVELOPMENT ANURIDA. 


——o 
ss 


<4 
i. 


oe 


i 


x 


Tio 


Seer 


B. Meisel, lith. Beston 


"a3 
rc 
fy 
= 
=a 


) 


Fo.tsom. — Development Anurida. 


PLATE 6. 


30. Transverse slightly oblique section of head at Stage 8.  X 480. 

. Dorsal aspect of left mandible of adult. > 150. 

. Dorsal aspect of anterior extremity of adult right mandible. X 480. 

. Dorsal aspect of skeletal structure of internal mouth-parts in situ. XX 160. 
. Dorsal aspect of head of left maxilla in adult. Xx 480. 

. Surface view of finished labrum. > 150. 

. Head of adult insect viewed from the left side. X 150. 


IDA. 


NUR 


A 


i 
i 


FoLSOM- DEVELOPMEN 


B 
oe 
ye 
Pe) 

& 
ue 
8 
= 
& 
~ 
SS 
> 
Ao 
= 
a 
Us eee i es 
ae i 
oe \ } ' 
"oy 
S ; = ms 
== ; acl ke 
S = 
S Mies 
Ss iS 


is 


* 


Foutsom. — Development Anurida. 


PLATE 7. 


Fig. 42. Dorsal aspect of completed lingua and superlingue. x 480. 

Fig. 43. Surface view (ventral) of adult labium. X 150. 

Figs. 44-50. Transections of internal mouth-parts of adult to show their relations 
to each other and to the buccal cavity. 

Fig. 44 is the most anterior of the series ; Fig. 50 the most posterior. 

Figs. 44 and 45 are magnified 350 diameters, Figs. 46-50, 480 diameters. 


FoLsoM.- DEVELOPMENT ANURIDA. PLATE. 7. 


‘ny 


. 


cav. buc 


JW. del. : B. Meisel, lith. Boston. 


“4 ; ; : 
it a D = : 7 = 


: - x . 
hs) Ree Re RTP 7 2 
mets oe —— i 
: ay § apa! ho J ee . ie = - : ay, : 
! : — " [ = 
a - "¢ - 
- : _ 
: - 
=. © - 7 
ve 
2 . 
: 7 A 
*N. a 
be ¥ * 
J 
Ro es 7 ie : 
7 = C Oe eS 
° 7 
g x Sas ———e 
; 7 os 
) » Zz ————— 
7 7 ‘ 
~ . 
* fs - ‘ 7 
; ony = 
7 5 on . = 
7 ; a 
~~ 
- fe as - 
' a - 4 
4 | 
> - 4 —{ 
: - 
7 — 
: 7 - " = * 
= ’ 
7 re | ae 
\ ae — - ~ f Me ' j a 
wee nue a i i i : 


Fousom. — Development Anurida. 


PLATE 8. 


Fig. 51. Reconstruction of part of the left side of the adult head, from sections 
taken near the median plane. X 350. 


PLATE 8, 


FOLSOM-DEVELOPMENT ANURIDA. 


tH il 7. ?, 
‘ Ubu, Bs 
aoa Hi _cesaneenaam POD ees if g Ul 
twhp i 
ER en mh ane nwtesTieyits Alpes ! 
POD teeta sauna eaen nay gene ; ' i 
uy ‘ i ) ‘, { \ POO 


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; 


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200 qo8 


= SSeS 


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B. Meisel, ith. Baston 


JW. del. 


The following Publications of the Museum of Comparative Zoology 
are in preparation : — 


‘Reports on the Results of Dredging Operations in 1877, 1878, 1879, and 1880), in charge of ALEX- 
ANDER AGASssiz, by the U. S. Coast Survey Steamer ‘ Blake,” as follows: — 


. EHLERS. 


. LUDWIG. The Genus Pentacrinus. 


bb mob 


. E. VERRILL. 


The Aznelids of the ‘‘ Blake.” 
HARTLAUB. The Comatule of the ‘‘ Blake,’ with 15 Plates, 


. MILNE EDWARDS and E. L. BOUVIER. The Crustacea of the “ Blake.” 
The Alcyonaria of the ‘‘ Blake.” 


Reports on the Scientific Results of the Expedition to the Tropical Pacific, in charge of 
ALEXANDER AGASSIZ, on the U.S. Fish Commission Steamer “‘ Albatross,” from August, 
1899, to March, 1900, Commander Jefferson F. Moser, U.S. N., Commanding. 


Illustrations of North American MARINE INVERTEBRATES, from Drawings by BuRK- 
HARDY, SONREL, and A, AGASSIZ, prepared under the direction of L, AGASS1zZ. 


LOUIS CABOT. 
E. L. MARK. 
=e On Arachnactis. 


Immature State of the Odonata, Part 1V. 
Studies on Lepidostens, continued. 


R. T. HILL. On the Geology of the Windward Islands. 
W. McM. WOODWORTH. On the Bololo or Palolo of Fiji and Samoa. 


A. AGASSIZ and A. G. MAYER. 


AGASSIZ and WHITMAN. Pelagic Fishes. 


The Acalephs of the East Coast of the United States, 


Part I1., with 14 Plates. 


Reports on the Results of the Expedition of 1891 of the U. 8. Fish Commission Steamer 
““ Albatross,” Lieutenant Commander Z, L. TANNER, U.S. N., Commanding, in charge of 


ALEXANDER AGASSIZ, as follows: — 


A. AGASSIZ. The Pelagic Fauna. 
= The Echini. 


“s The Panamic Deep-Sea Fauna. 


K. BRANDT. The Sagitta. 
ae The Thalassicola. 


C. CHUN. ‘The Siphonophores. 
so The Eyes of Deep-Sea Crustacea. 
W. iH. DALL. The Mollusks. 


H. J. HANSEN. The Cirripeds. 

W. A. HERDMAN. The Ascidians. 

S. J. HICKSON. The Antipathids. 

W. E. HOYLE. The Cephalopods. 

G. VON KOCH. The Deep-Sea Corals. 

C. A. KOFOID. Solenogaster. 

R. VON LENDENFELD. ‘The Piospiio- 
rescent Organs of Fishes. 


H. LUDWIG. The Starfishes. 

J.P. McMURRICH. The Actinarians. 

E. L. MARK. Branchiocerianthus. 

JOHN MURRAY. ‘The Bottom Specimens. 

ROBERT RIDGWAY. The Alcoholic Birds. 

P. SCHIEMENZ. The Pteropods and Hete- 
ropods. 

L. STEJNEGER. The Reptiles. 

THEO. STUDER. ‘The Alcyonarians, 

M. P. A. IRAUTSTEDT, The Salpide and 
Doliolide. 

E. P. VAN DUZEE. ‘The Halobatide. 

H. B. WARD. ‘The Sipuneulids. 

H. V. WILSON. The Sponges. 

W. MoM. WOODWORTH. The Nemerteans, 

ss The Annelids. 


PU BEC ATLONS 


OF THE 
MUSEUM OF COMPARATIVE ZOOLOGY 


AT HARVARD COLLEGE. 


There have been published of the BuLLETIns Vols. I. to XXXYV.; 
of the Memoirs, Vols. I. to XXIV. 

Vols... XXXVI., XXXVII., and XXXVIII. of the BuLierm, 
and Vols. XXV., XXVI. of the Memoirs, are now in course of 
publication. 

The Butiterin and Memoirs are devoted to the publication of 
original work by the Professors and Assistants of the Museum, of 
investigations carried on by students and ethers in the different 
Laboratories of Natural History, and of work by specialists based 
upon the Museum Collections and Explorations. 


The following publications are in preparation : — 


Reports on the Results of Dredging Operations from 1877 to 1880, in charge of 
Alexander Agassiz, by the U. S. Coast Survey Steamer “ Blake,” Lieut. 
Commander C, D. Sigsbee, U. S. N., and Commander J. R. Bartlett, U.S. N., 
Commanding. 

Reports on the Results of the Expedition of 1891 of the U.S. Fish Commission 
Steamer ‘“ Albatross,” Lieut. Commander Z. L. Tanner, U. S. N., Com- 
manding, in charge of Alexander Agassiz. 


Reports on the Scientific Results of the Expedition to the Tropical Pacific, in 


charge of Alexander Agassiz, on the U.S. Fish Commission Steamer 
“ Albatross,” from August, 1899, to March, 1900, Commander Jefferson F. 
Moser, U. S. N., Commanding. 

Contributions from the Zodlogical Laboratory, in charge of Professor E. L. 
Mark. 

Contributions from the Geological Laboratory, in charge of Professor N. S. 
Shaler. 


Subscriptions for the publications of the Museum will be received 
on the following terms : — , 


For the Butterr, $4.00 per volume, payable in advance. 
For the Memoirs, $8.00 oe ee oe 


These ‘publications are issued in numbers at irregular inter- 
vals; one volume of the Bulletin (8vo) and half a volume of the 
Memoirs (4to) usually appear annually. Each number of the Bul- 
letin and of the Memoirs is also sold separately. A price list 
of the publications of the Museum will be. sent on application 
to the Librarian of the Museum of Comparative Zodlogy, Cam- 
bridge, Mass. 


Ps 


ERA SASE Bes Oe AE RTS ee Oe REN ON tae, as fe Se RO ee, VS ee re ee 


ma Se en, 


ww yu vy Mf 


bt:'] oe 


Bulletin of the Museum of Comparative Zoology 
AT HARVARD COLLEGE, 
Vout. XXXVI. No. 6. 


REPORTS ON THE DREDGING OPERATIONS OFF THE WEST CGAST FP 
CENTRAL AMERICA TO THE GALAPAGOS, TO THE’ WEST, ;COAST 
OF MEXICO, AND IN THE GULF OF CALIFORNIA, IN CHARGE OF 
ALEXANDER AGASSIZ, CARRIED ON BY THE U. S. FISH, COMMIS: 
SION STEAMER “ALBATROSS,” DURING 1891, LIEUT. COMMANDER 
Z. L. TANNER, U.S. N.,. COMMANDING. 


XXVIII. 


DESCRIPTION OF TWO NEW LIZARDS OF THE GENUS ANOLIS FROM 
COCOS AND MALPELO ISLANDS. 


By LEONHARD STEJNEGER. 


[Published by Permission of MARSHALL McDONALD and GEORGE M. BowERs, 
U. §. Fish Commissioners. | 


With One PLATE. 


CAMBRIDGE, MASS., U.S. A.: 
PRINTED FOR THE MUSEUM. 


Novemeper, 1900. 


, 


ee 


c 
. 


et, 


atf 


‘ 


1 
4 
Kbaux 


tt et 


Bulletin of the Museum of Comparative Zoology 
AT HARVARD COLLEGE. 
Vor. XXXVI: No..6. 


® 


REPORTS ON THE DREDGING OPERATIONS OFF THE WEST COAST OF 
CENTRAL AMERICA TO THE GALAPAGOS, TO THE WEST COAST 
OF MEXICO, AND IN THE GULF OF CALIFORNIA, IN CHARGE OF 
ALEXANDER AGASSIZ, CARRIED ON BY THE U. S. FISH COMMIS- 
SION STEAMER “ALBATROSS,” DURING 1891, LIEUT. COMMANDER 
Z. L. TANNER, U.S. N., COMMANDING. 


XXVIII. 


DESCRIPTION OF TWO NEW LIZARDS OF THE GENUS ANOLIS FROM 
COCOS AND MALPELO ISLANDS. 


By LEONHARD STEJNEGER. 


[Published by Permission of MARSHALL McDoNALD and GEORGE M. BowERs, 
U. S. Fish Commissioners. ] 


WitH OnE PLATE. 


CAMBRIDGE, MASS., U.S. A. : 
PRINTED FOR THE MUSEUM. 


NovemBer, 1900. 


=H? 


No. 6.— Report on the Dredging Operations off the West Coast 
of Central America to the Galapagos, to the West Coast of 
Mexico, and in the Gulf of California, in charge of Alexander 
Agassiz, carried on by the U. S. Fish Commission Steamer 
“ Albatross,’ during 1891, Linut. COMMANDER Z. L. TANNER, 
U.S. N., Commanding. 


XXVIII. 


Description of two new Lizards of the genus Anolis from Cocos and 
Malpelo Islands. By LronnarD STEJNEGER. 


The two Anoles here described were the only reptiles obtained on the 
islands of Cocos and Malpelo during the expedition. ach species is 
peculiar to the island upon which it is found. Of the two, the one from 
Malpelo seems to be most highly specialized, there being no nearly 
related species on the mainland with which I am familiar, while the 
species from Cocos Island belongs to a group which has a number of 
representatives in Central America. The two species are only distantly 
interrelated, inasmuch as they belong to widely separated sections of 
the genus. 

It is quite possible that a more thorough search on Cocos Island 
might reveal additional reptiles. In fact, Mr. Townsend informs me 
that he saw a snake there which escaped. 


Anolis agassizi,' sp. nov. 


Diagnosis. — Tail cylindrical, without crest or keel; dorsal scales keeled, 
subequal to those on the flanks, slightly smaller than the ventrals, and 
separated from each other by one or more rows of minnte granules ; 
ventral scales keeled ; digital expansions very large ; about thirty-six trans- 
verse lamellz under ii and ili phalanges of fourth toe: occipital scale 
about as large as ear-opening; scales of supraorbital semicircles very much 
enlarged (forming high, tuberculated crests in the adults), and separated by 
one row of small scales; occipital separated from supraorbital semicircles by 
one or two series of scales; supraocular scales rough or rugose, sometimes 
irregularly keeled ; canthus rostralis sharp; mental shield single, with a deep 
suleus posteriorly, very large ; tibia nearly equalling the head in length, and at 


1 Named in honor of Professor Alexander Agassiz. 
VOL. XXXVI. — NO. 6. 


162 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


least as long as distance from mouth to ear-opening ; scales on under side of 
tail twice as large as those on the upper side, all keeled ; scales on dorsal surface 
of hands and feet multi-carinate. Adults with a high longitudinal cervico- 
nuchal flap ; males with enlarged post-anal scales. 

Halitat. — Malpelo Island, Pacific Ocean, off Columbia, South America. 

Type. — U. S. National Museum, No 22101; March 5, 1891; collector, 
Chas. H. Townsend. 

Description. — g ad. U.S. Nat. Mus. No. 22101. Head once and two thirds 
as long as broad, slightly longer than tibia; frontal and occipital regions deeply 
concave ; supraorbital ridges high, bony, surrounding the occipital hollow, and 
nearly joining behind it at the beginning of the cervico-nuchal fold; anteriorly 
they divide and continue mesially as frontal ridges which converge on the 
snout, meeting some distance behind the level of the nostrils, while externally 
they join the supraciliary ridge, and in company the latter extend to under the 
nostrils as a strong canthus rostralis, thus forming a deep valley on each side 
between the canthus and the frontal ridge; there is also a post-superciliary 
ridge extending to above the ear-opening, and with a valley between it and 
the occipital ridge; scales of supraorbital semicircles very much enlarged, 
forming high tuberculated bony crests, separated by a single series of very 
small scales; scales forming frontal ridges and valleys rather large, irregu- 
larly hexagonal, concave or convex according to situation; scales on snout 
smaller, more irregular, elongate, four in contact with rostral; about seven 
larger supraocular scales, keeled or tuberculated, separated by one row 
of granules from semicirculars; superciliary edge with two very elongated 
scales anteriorly, granular posteriorly; occipital scale slightly larger than ear- 
opening, separated from supraorbital semicircle by one row of scales; three 
canthal scales ; loreal region with two deep hollows, the posterior one largest ; 
loreal rows four; a series of large suboculars, of which the one below the 
posterior angle of the eye descends to the edge of the lip; rostral very wide 
and very low, four times as wide as high, nearly rectangular ; six to seven low 
supralabials in front of the subocular edging the lip, decreasing in height poste- 
riorly; ear-opening rather small, oval, vertically oblique; nape and neck with 
a high, flexible dermal crest or flap on the middle line, almost co-extensive 
with the poorly developed dewlap underneath; several dermal folds and 
wrinkles on sides of neck ; mental shield large, with a deep sulcus behind ; 
gular scales small, feebly keeled ; body feebly compressed ; dorsal scales 
slightly larger than those on flanks, a few series along the median line de- 
cidedly, though not abruptly larger, all more or less distinctly keeled and sur- 
rounded by one or more minute granules; ventral scales slightly larger than 
dorsals, rhomboidal, imbricate, keeled, about five to six in the distance between 
nostrils ; scales on anterior surfaces of limbs larger than ventrals, keeled, those 
on dorsal surface of hands and feet multi-carinate; adpressed hind limb 
reaches halfway between eye and nostral; digital expansions very large, 
thirty-six transverse lamellae under ii and iii phalanges of fourth toe; 
tail less than twice the length of head and body, cylindrical, without crest or 
keel; scales on tail larger than ventrals, straight, in transverse rows, but with 


STEJNEGER: LIZARDS FROM COCOS AND MALPELO ISLANDS. 163 


scarcely an indication of verticels, those on the lower surface nearly twice as 
large as those above ; a pair of enlarged post-anal scales. Color of live speci- 
men (according to the sketch of Mr. Magnus Westergrer, the artist of the 
expedition): top and sides of head and neck uniform sooty black gradually 
merging into the ground color of the upper surface of body, which is “ Van- 
dyke ’’ brown, sprinkled with minute. dots of an ochraceous buff; upper sur- 
face of limbs as well as alternate cross-bands on tail similarly colored ; the 
hands and feet as well as the intervals between the crossbands pale “ Nile” 
blue; end of snout, lips, and entire under side similarly bluish white. In 
alcohol the ground color is more blackish and the dots less yellowish. 


DIMENSIONS. 
otalileng thee yma men yee neun tse eul-ne uf) ANI 
SHCMy UO Chee Mg le tp 6 6 p 4 6 Ha & 
Snout to vent ee a eh ene ees LOTR 
eRaristromeventamery st ahem cc. hh. e) ee ete os Oh s 
Horeylimba sey ees ta eee ee ee ae ELIE ce 
Etindlimibs yeaa ab isnt ress 4 ee FR COOH 
eiibiaarie Mier wr ery Bae ltp eee te) Foie Mg. dae tOG4. ie 


Variation. — A large full-grown female (No. 22103) differs from the male 
described above only in the absence of enlarged post-anal scales. Two some- 
what younger specimens (female, No. 22104, male, No. 22105) differ from 
the fully adult specimens chiefly in the lesser elevation of the cephalic crests 
and the total absence of the cervico-nuchal flap; the color of the back, which 
seems to be identical with that of the adults, extends also over the upper 
surface of neck and head. 

Remarks. — Mr. Charles H. Townsend, who collected these specimens in 
Malpelo, informs me that they were running over the rocks near the water. 
The island was too steep to afford a landing, but the lizards were shot off or 
whisked off the face of the cliffs, thus falling into the water, whence they 
were secured by the collector. 


Anolis townsendi,! sp. nov. 


Diagnosis. — Tail subcylindrical ; dorsal scales but indistinctly larger than 
those on the flanks, those on the vertebral region keeled ; gular and ventral 
scales keeled ; digital expansion strongly developed ; occipital scale larger than 
ear-opening, separated from supraorbital semicircles by two or three scales, the 
semicircles separated by a similar number of scales ; scales on upper surface of 
snout as well as enlarged supraoculars keeled; anterior half of superciliary 
ridge with three very long and narrow, strongly keeled scales placed obliquely ; 
no markedly enlarged series of scales below infralabials ; tibia measuring more 
than two thirds the length of head, slightly shorter than distance between end 
of snout and ear-opening; the adpressed hind limb reaches beyond the eye ; 
tail more than once and a half as long as head and body. 


1 Named in honor of Mr. Charles H. Townsend. 


164 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


Habitat. — Cocos Island, Pacific Ocean, off Costa Rica, Central America. 

Type. —U. S. National Museum, No. 22106; Feb. 28, 1891; collector, 
Charles H. Townsend. 

Description. — g ad. U.S. Nat. Mus. No. 22106. Head twice as long as 
broad, longer than tibia; forehead slightly concave; frontal ridges nearly 
obsolete; upper head scales small, keeled ; scales of supraorbital semicircles 
moderately enlarged, separated by three scales; enlarged supraorbitals numer- 
ous, elongated, sharply keeled, in contact with semicirculars ; occipital shield 
elongate oblong, somewhat larger than ear-opening, separated from semicircu- 
lars by two scales; canthus rostralis very distinct, of six scales, the anterior 
ones small, the posterior two very long and narrow continued backwards in 
line with three superciliaries, which are also unusually long, narrow, and 
keeled ; posterior half of superciliary ridge granular ; a series of enlarged sub- 
oculars, keeled, not reaching lip ; loreal rows, about six, keeled ; eight supra- 
labials to below centre of eye, rugose ; ear-opening moderate, vertically oval ; 
dewlap moderate with a thickened edge of densely set short thick scales, those 
on sides of appendage distant and very elongate; gular scales small, long, and 
narrow ; dorsal scales much smaller than ventrals, and indistinctly larger than 
those on the flanks, and gradually but slightly increasing in size toward the 
vertebral line, where a few rows are distinctly keeled; no dorsal or cervical 
fold or crest; ventral scales larger, imbricate, keeled, like all the scales of the 
underside ; scales on anterior surfaces of limbs somewhat larger than ventrals, 
keeled ; tail subeylindric, scales about the size of ventrals, keeled, with 
hardly an indication of verticels; body compressed ; adpressed hind limb 
reaches heyond eye ; no enlarged post-anal scales. Color above dull brownish 
gray, irregularly and indistinctly mottled with dusky which shows a tendency 
to form cross-bars on the tail; limbs more brownish with lighter roundish 
spots ; lores, temples, and sides of neck anteriorly with irregular white mark- 
ings ; a very distinct white, black-edged lateral band from sides of neck over 
the shoulder to groin; underside whitish ; throat with indistinct, brownish 
mottlings. 


DIMENSIONS. 
AN selg G5 b 610 905 @ oo o We ra, 
Snout toiear-opening» =... -gueu een Loni 
Snoutstosvient: < sch cos col n)e Omer Rein ne a 
Tailtromevent,: 10h) Qe ie Soeeiee ee. eee OMe 
Rorelimb: “(scene ee ee kena oe 
indatimibt “3 shee ee ee eee eee) re Coes 
AOE: ered Ra mRNA ELS) is edt ee ee TIARA 


Variation. — A slightly smaller female (U. S. Nat. Mus. No. 22107) differs 
chiefly in the absence of a dewlap and in coloration ; the white lateral band is 
present, but it is not edged with blackish, and there is in addition a narrow 
white vertebral band from occiput to root of tail. 


TOOT VAT CRON TWAT 


THE FOLLOWING REPORTS HAVE BEEN PUBLISHED OR ARE IN PREPA- 


RATION ON THE DREDGING OPERATIONS OF THE U. S. Fisu Com- 


MISSION STEAMER “ ALBATROSS 


,” DURING 1891. 


A, AGASSIZ. II.1 General Sketch of the 
Expedition of the ‘ Albatross,” from 
February to May, 1891. 

A. AGASSIZ. The Pelagic Fauna. 

A. AGASSIZ. The Deep-Sea Panamic Fauna. 
A, AGASSIZ. I.2 On Calamocrinus, a new 
Stalked Crinoid from the Galapagos. 

A. AGASSIZ. XXIII.23 The Echini. 

R. BERGH. XIII.18 The Nudibranchs. 

K. BRANDT. The Sagitta. 

K. BRANDT. The Thalassicole. 

C. CHUN. The Siphonophores. 

C. CHUN. The Eyes of Deep-Sea Crustacea. 

S. F. CLARKE. XI. The Hydroids. 

W. H. DALL. The Mollusks. 


W. FAXON. VIS XV. The Stalk-eyed 
Crustacea, 


S. GARMAN. XXVI.% The Fishes. 
W.GIESBRECHT. XVI.15 The Copepods. 
A. GOES. IIIL* XX.% The Foraminifera, 
H. J. HANSEN. The Cirripeds. 

H. J. HANSEN. XXII.% The Isopods. 

C. HARTLAUB. XVIII.!8 The Comatule. 
W. A. HERDMAN. The Ascidians. 

S. J. HICKSON. The Antipathids. 

W. E. HOYLE. The Cephalopods. 

G. yon KOCH. The Deep-Sea Corals. 

C. A. KOFOID. Solenogaster. 


R. yon LENDENFELD. The Phosphores- 
cent Organs of Fishes. 


H. LUDWIG. IV.5 XII. The Holothu- 
rians. 


H. LUDWIG. The Starfishes. 


Cc. F. LUTKEN and TH. MORTENSEN. 
XXV.25 The Ophiurida. 


OTTO MAAS. XXI.21 The Acalephs. 
J. P. McMURRICH. The Actinarians. 
E. L. MARK. XXIV.2! Branchiocerianthus. 


GEO. P. MERRILL. V.° The Rocks of the 
Galapagos. 


G. W. MULLER. XIX. The Ostracods. 
JOHN MURRAY. The Bottom Specimens. 


A. ORTMANN. XIV. The Pelagic Schi- 
zopods. 


ROBERT RIDGWAY. The Alcoholic Birds. 
P. SCHIEMENZ. The Pteropods and Het- 


eropods. 

W. SCHIMKEWITSCH. VIII The Pyc- 
nogonide. 

S. H. SCUDDER. VII.7’ The Orthoptera of 


the Galapagos. 
L. STEJNEGER. XXVIII.22 The Reptiles. 
TH. STUDER. X.!° The Alcyonarians. 


C. H. TOWNSEND. XVII." The Birds of 
Cocos Island. 


M. P. A. TRAUTSTEDT. The Salpida and 
Doliolide. 


E. P. VAN-DUZEE. The Halobatide. 
H. B. WARD. The Sipunculoids. 
H. V. WILSON. The Sponges. 


W.McM. WOODWORTH. IX. 
narians and Nemerteans. 


WwW. McM. WOODWORTH. 
Planktonemertes. 


W. McM. WOODWORTH. The Annelids. 


The Pla- 


XXVII.27 


1 Bull. M.C. Z., Vol. XXI., No. 4, June, 1891, 16 pp.; and Vol. XXTII., No. 1, February, 1892, 


89 pp., 22 Plates. 
2 Mem. M. C. Z., Vol. 
Bull. M. = 2.8.4 Rigee 
Bull. M. C. Z., Vol. 
Bull. M. 


3 
a 
6 
6 Bull. M. C. Z., Vol. 
7 
8 
9 


Bull. M. C. Z., Vol. XXV-, 
Bull. M. C. Z., Vol. XXV., No 


Bull. M. C, 
10 Bull. M. C., Z. . XXV.; No 
11 Bull, M. C. Z., Vol. 


. XXV., No 


XVII., No. 2, January, 1892, 95 PP» 32 Plates. 
No, 7, August, 1893, 72 pp. 

XXIII., No. 5, December, 1892, 4 pp., 1 Plate. 
. XXIV., No. 4, June, 1893, 10 pp. 
XVI., No. 13, July, 1893, 3 pp 
No. 1, September, 1893, 25 pp. 

. 2, December, 1893, 17 pp., 2 Plates. 
. 4, January, 1894, 4 pp., 1 Plate. 

. 5, February, 1894, 17 pp. 

6, February, 1894, 7 pp., 5 Plates. 
8, September, 1894, 13 pp., 1 Plate. 
10, October, 1894, 109 pp , 12 Plates. 


[Zool. Anzeig., No. 420, 1893.) 


19 Plates. 


. XXIX., No. 1, March, 1896, 103 pp., 9 Plates, 1 Chart. 


XXV., No. 
12 Bull. M. C. Z., Vol. XXV., No. 
13 Bull. M. C. Z., Vol. XXV., No. 
14 Mem. M. C. Z., Vol. XVII., No. 3, October, 1894, 183 pp., 
15 Bull. M. CG. Z., Vol. XXV., No. 12, April, 1895, 20 pp., 4 Plates. 
16 Mem. M. C. Z., Vol. XVIII., April, 1895, 292 pp., 67 Plates, 1 Chart. 
17 Bull. M. C. Z., Vol. XXVII., No. 3, July, 1895, 8 pp., 2 Plates. 
13 Bull. M. C. Z., Vol. XXVII., No 4, August, 1895, 26 pp., 3 Plates. 
19 Bull. M. C. Z., Vol. XXVII., No. 5, October, 1895, 14 pp., 3 Plates. 
20 Bull. M. C. Z., Vol 
21 Mem. M. C. Z., Vol. XXIII., No. 1, September, 1897, 92 pp., 15 Plates. 
22 Bull. M. C. Z., Vol. 


23 Bull. M. C. Z., Vol. 

24 Bull. M. C. Z., Vol. 

25 Mem. M. C. Z., Vol. 

26 Mem. M. C. Z., Vol. XXIV., 
27 Bull. M. C. Z. 

28 Bull. M. C. Z. 


XXXI., No. 5, December, 1897, 37 pp., 6 Plates, 1 Chart. 
XXXII., No. 5, May, 1898, 18 pp., 13 Plates, 1 Chart. 
XXXII., No. 8, August, 1898, 8 pp., 3 Plates. 

XXII., No. 2, November, 1899, 116 pp.. 22 Plates, 1 Chart. 
= December, 1899, 431 pp., 97 Plates, 1 Chart. 

., Vol. XXXV., No. 1, July, 1899, 4 pp., 1 Plate. 

, Vol. XXXVI., No. 6, November, 1900, 6 pp., 1 Plate. 


PUBLICATIONS 


OF THE 


MUSEUM OF COMPARATIVE ZOOLOGY 
AT HARVARD COLLEGE. 
There have been published of the ButLetins Vols. L to XXXV.; 


of the Memoirs, Vols. I. to XXIV. 
Vols. XXXVI, XXXVIL., and: XXXVIII. of the Burrerm, 


and Vols. XXV., XXVI. of the Mrmorrs, are now in course of | 


publication. 

The Buiierin and Memoirs are devoted to the publication of 
original work by the Professors and Assistants of the Museum, of 
investigations carried on by students and others in the different 
Laboratories of Natural History, and of work by specialists based 
upon the Museum Collections and Explorations. 


The following publications are in preparation : — 


Reports on the Results of Dredging Operations from 1877 to 1880, in charge of 
Alexander Agassiz, by the U. S. Coast Survey Steamer “ Blake,” Lieut. 
Commander C. D. Sigsbee, U. S. N., and Commander J. R. Bartlett, U.S.N., 
Commanding. 

Reports on the Results of the Expedition of 1891 of the U.S. Fish Commission 
Steamer “ Albatross,” Lieut. Commander Z. L. Tanner, U. 8S. N., Com- 
manding, in charge of Alexander Agassiz. 

Reports on the Scientific Results of the Expedition to the Tropical Pacific, in 
charge of Alexander Agassiz, on the U.S. Fish Commission Steamer 


“ Albatross,” from August, 1899, to March, 1900, Commander Jefferson F. 


Moser, U.S. N., Commanding. 

Contributions from the Zodlogical Laboratory, in charge of Professor E. L. 
Mark. 

Contributions from the Geological Laboratory, in charge of Professor N. S. 
Shaler. 


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an 


oy, ae 


ae Vee SS 


th 


Bulletin of the Museum of Comparative Zoology 
AT HARVARD COLLEGE. 
Von, come Vis: No. 7. 


THE OTOCYST OF DECAPOD CRUSTACEA: ITS STRUCTURE, 
: DEVELOPMENT, AND FUNCTIONS. 


By C. W. PRENTIsS. 


Wirtn Ten PLates. 


CAMBRIDGE, MASS., U.S.A.: 
PRINTED FOR THE MUSEUM. 
Jury, 1901. 


No. 7. — Contributions from the Zodlogical Laboratory of the 
Museum of Comparative Zodlogy at Harvard College, under 
the direction of E. L. Mark, No. 123. 


THE OTOCYST OF DECAPOD CRUSTACEA: ITS 
DEVELOPMENT, AND FUNCTIONS. By C. W. 


Introduction 


Part I.— Morphology . 
A. Historical Survey 


B. Observations . 


1. Material. . 
2. Methods. . OG pe ld 
3. Structure and Development 


I. Paleemonetes . 


1. 


to 


co 


Structure of the 
Otocyst 

i SEG 5 6 > 

6. Sensory Cushion 

c. Structure of 
Hairs . 

d. Formation of 
skits) 6 6 6 

ec Otoliths’.) ec 


. Innervation of the 


Otocyst 

a. Number of 
Nerve Ele- 
ments to a 
Single Bristle 

6. Peripheral Ter- 
minations 

c. Central Termi- 
nations 

d. Histology of 
the Nerve Ele- 
ments . 


- Development of 


the Otocyst. 
(In Homarus 
americanus.) 
a. 1st larval Stage 
Doda e 


C. 
Gpatday OC al 
é. 


PAGE 


180 
180 
180 
181 
182 


182 
184 


185 


186 


188 


190 


191 


VOL. XXXVI. —NO. 7 


II. Crangon 196 | III. 


PAGE 


TABLE OF CONTENTS. 


STRUCTURE, 
PRENTISS. 
PAGE 
eel Gs 
a aia Hay) 
5 1G) 
177 
iets 
178 
- 180 
PAGR PAGE 
200| IV. Carcinus 204 
200 205 
200 sit ee ore 205 
200 ae, ve 206 
201 208 
202 Soetoro lel: 
202 Oo oo. eel 
202 os 5 eel! 
203 AL tC 212 
203 OO 3 213 
203 au siecmeel 
204 5 213 
204 sHiventie 214 
Ist Zoea 214 
a ethd 2s 914 
ayel 214 
- - Megalops . 214 
- - Youngcerab 214 


168 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


PAGE 
C. Theoretical Considerations. . . 215 


1. Comparison of the Otocyst with the Vertchrae Ear 215 
2. Neuronsiheory, ©, = felis tsas sihensenem namely 


Part IT: —Physiologys,< 7 | < 2s," c. <euien eet Ones 


PAGE PAGE 
A. Historical Survey . . . 5 6 Pals! c. Both Eyes blinded and 
B. Experiments and Observations - 2238 both Otocysts removed . 230 
I. The Otocyst as an ere te Or- d. One Eye blinded and both 
Gai sweaters > . 223 Otoeysts removed . 231 
Methods assume 223 e. Both Eyes blinded ale one 
1. Responses of Palemoncees ts Otocyst removed . .. . 231 
Vibrations transmitted to 2. Removal of Sense Organs 
Water .. - « - 223 and its Effect on the Com- 
a. Normal Gandiionn So PPB! pensation Movements of the 
6. Poisoned with Strychnine 224 IDS Go 6 Newtons 
c. Both Otocysts removed . 224 a. Normal eee « 2 0 « 23e 
d. Removal of Antenne and 6. Both Eyes blinded . . . 2382 
both Antennules . . . . 224 c. Both Otocysts removed . 233 
e. Meaning of these aaa d. Both Eyes blinded and 
THEHES (aes 225 both Otocysts removed . 233 
2. Responses of Gata: see 3. Equilibration of Animals nor- 
FARO 5 6 226 mally without Otocysts . . 234 
a. To Wabentinnen fount 4. The Effect of the Develop- 
to Water .. . 226 ment of the Otocyst on the 
6. To Atmospheric Scents - 227 Equilibration of Lobster 
Il. The Otocyst as an Organ of Larve . 234 
Equilibration es 228 5. The Function of ‘the Otoliths 237 
1. The Removal of Sense On 6. The Function of the Hairs of 
gans and its Effect on Equil- the Otocyst’ “2 ee) sseemne et 
ibration . . “ 2 « « 230 | Summary «: =‘ (c) 20s) (onions 
@. Hyves blinded = = © < . 280) | Bibliography, . = <9. enieeneeeecan 
b. Both Otocysts removed . 230 | Explanation of Plates . PEM ey Pa 


INTRODUCTION. 


Srnce the appearance of the admirable paper by Hensen (’63) on the 
auditory organs of decapods, a period of thirty-seven years has elapsed, 
a period rich in zodlogical discoveries and improvement in general tech- 
nique. The great advances made in comparative neurology by means 
of modern methods have reopened to investigators fields for research 
hitherto considered exhausted. The zodlogist of the present time is 
thus enabled to reap a second crop on ground already carefully gleaned, 
and to harvest results as important as those originally obtained. 

The physiological work of Hensen’s paper has been continued in re- 
cent years by various investigators. But aside from the paper by 
Bethe (’95) on the otocysts! of the schizopod Mysis, little work has 
been done on the morphology of the decapod ear since 1863. 


1 Throughout this paper the terms otocyst, statocyst, ear, and auditory sac 
will be used synonymously to designate the auditory organ, so-called, of Crustacea. 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 169 


To throw more light on our knowledge of the vertebrate ear, com- 
parative study of the (perhaps) analogous organ found among inverte- 
brates may be of great practical value. For by such comparative 
study zodlogists have been enabled to solve many perplexing questions 
which might otherwise have proved too difficult for solution. 

The present study was undertaken with this practical bearing of the 
subject in mind, and with the hope that by the aid of modern neurologi- 
cal technique it would be possible to go deeper into many undecided 
questions than Hensen could. 

The work is necessarily twofold in its scope, owing to the inseparable 
nature of the morphology and physiology of the auditory organ. We 
have, first, to obtain more accurate knowledge concerning the structure, 
innervation, and development of the decapod otocyst. In doing this 
especial attention must be given to the innervation, which must be com- 
pared with that of other sense organs in decapods. And, secondly, 
we must determine from evidence obtained by others in the past, and 
from additional physiological experiment, whether we are justified in 
ascribing a true auditory function to this much discussed apparatus. 


PART I. — MORPHOLOGY. 


A. HISTORICAL SURVEY. 


Although the literature up to Hensen’s time is well summarized by 
him, yet it may be worth the while to take a glance at what has been 
done, touching upon only the more important works, however, as a fairly 
complete list of authors is appended in the Bibliography. 

The earliest notice of an ear in Crustacea is that of Minasi, a Domini- 
can monk, who in 1775 attributed the sense of hearing to Pagurus, the 
hermit crab, and described as the auditory apparatus what is now known 
as the green gland or excretory organ of decapods. The organ supposed 
to subserve the function of hearing was thus from the very first mis- 
placed, and its identity was in doubt even up to the time of Hickel 
(57) and Leydig (’57), who were the first to rectify the erroneous ideas 
which existed in regard to the functions of the green gland and the 
otocyst. 

The true sacs were, however, discovered and described as early as 
1811 by Rosenthal (11), He mentions the cavity, its opening, and 
nerve; but it was left for Treviranus (’02-’22, Bd. 6, pp. 308-310) to 
discover the sand, or otoliths, present in the otic chamber. 


170 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


The first good description of the organ, accompanied by figures, was 
given by the Englishman Farre (’43), who carefully dissected the 
otocysts of the crayfish (Astacus fluviatalis), the European lobster 
(Astacus marinus), the hermit crab (Pagurus), and the rock lobster 
(Palinurus quadricornis). 

The organs were found by Farre to be situated in the basal segment 
of the inner antenn (antennules), the thin dorsal membrane of which 
in A. marinus he compared to the fenestra ovalis of the vertebrate ear. 
The openings of the sacs were always found to be large enough to admit 
the otoliths, which rest upon auditory bristles. The otoliths were, he 
maintained, merely grains of sand. The auditory bristles were briefly 
described, and their semi-circular arrangement noted; a nerve was 
traced from the brain to the ventral surface of the otocyst, where it 
formed a plexus. In Farre’s opinion separate fibres probably supplied 
the bases of the different hairs. While the otocysts of the lobster, 
crayfish, and hermit crab were of relatively large size, nearly filling the 
basal segment of the antennule, their openings were very small and 
well guarded by a “chevaux de frise” of bristles. In Palinurus the 
organ was apparently degenerate ; the sac small, shallow, with very large 
opening, and the auditory hairs sparse and irregularly arranged. The 
otoliths were of large size and few in number. The whole apparatus 
was held by Farre to be a delicately modified tactile organ, and he 
doubted if a true auditory function could be ascribed to it. 

During the next twenty-five years otocysts were discovered and ex- 
amined in various decapods by Souleyet (’43), Von Siebold (44, 748), 
Leuckart (’53, ’59), Frey und Leuckart (47), Huxley (51), Leydig (’55, 
’57, 60), Bate (’55, ’58), Hensen (63), Sars (’67), and Lemoine (68). 
Leuckart und Frey (47) briefly described the sacs which they found in 
the endopod of the last abdominal appendages of Mysis, mentioning 
the otolith and auditory hairs. 

Leuckart (’53) made a comparative study of the otocysts in many 
crustacean forms. He divided them into two groups : — Those having 
(1) closed sacs with one otolith, and (2) open sacs with many otoliths. 
Leuckart’s general descriptions agree with those of Farre. 

Kroyer (’59) devotes a few pages of his monograph on Sergestes to 
a comparative account of this organ in different Crustacea. He follows 
Leuckart’s method of grouping. To the first type (closed sacs, and one 
otolith) belong such forms as Lucifer, Sergestes, Mysis, and Phyllosoma. 
In the second group (open sacs and many otoliths) are placed Homarus, 
Astacus, and Palinurus. In the opinion of Kroyer, Farre erred in con- 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. LV: 


sidering the otoliths simply particles of sand; for sometimes the sacs 
are closed, and again the openings are often too smal] to admit the 
passage of the otoliths from the exterior. They must be, then, deposits 
of calcium carbonate secreted by the animals themselves. 

Hensen’s (’63) account of the otocyst is far more complete than any 
other, and a fairly extensive review of his paper is necessary for the 
sake of later comparisons. He worked mostly with freshly collected 
animals, although some twenty-four species were studied from alcoholic 
material. His principal methods were dissection and maceration, some 
few crude sections, however, being made. The paper is divided into an 
anatomical and a physiological part. The latter portion will be re- 
viewed, along with other papers of a similar nature, in Part II of this 
paper. 

The elementary parts of the typical auditory organ are described by 
Hensen (63, p. 326) thus: ‘Der Gehdrapparat der héheren Krebse 
besteht nun, kurz gesagt, darin, dass, von der Endganglie eines Nerven 
ein feiner Faden in ein Chitinhaar hineintritt, und an einen eigen- 
thiimlich gebildeten Theil der Haarwand sich festsetzt. Diese Haar- 
wand ist so locker mit der Schalenhaut verbunden, dass sie bei 
entsprechenden Ténen recht bedeutende Schwingungen vollfiihren kann 
und vollfiihrt. Das Haar selbst geht zuweilen noch in oder zwischen 
Steine hinein.” 

Crustacea he divides into four classes according to the condition of 
otocyst and otoliths :— 

1. Sacs closed, with one otolith : example, Mysis. 

2. Sacs closed, without an otolith: all Brachiura. 

3. Sacs open, many otoliths : Astacus, Paleemon. 

4, No sac nor otoliths, but free auditory hairs. 

Otoliths. In confirmation of Farre it was found that the otoliths of 
decapods having open ear sacs were mainly composed of grains of sand. 
This was proved by chemical tests, and by keeping newly moulted 
animals (Palemon) in filtered water to which uric acid crystals had 
been added. Examination of the otocysts some time after moulting 
showed the presence of these crystals in the sac. In larger forms, such 
as the lobster and crayfish, the sand particles are spread over the whole 
basal surface of the ear sac. In shrimps and prawns they are more 
closely aggregated. The single otolith found in Mysis flexuosus is 
described at length, but as this account has been corrected by Bethe 
(’95), it will be referred to later in connection with Bethe’s work. 

The Otocyst (Hérblase of Hensen) is described in general as a round- 


L72 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


ish or ovoid cavity, lined with chitin; the opening, if any, is always 
dorsal, and varies greatly in size. It is found in the basal segment of 
the first antenne of all decapods, and in the endopod of the sixth or last 
abdominal appendage of the schizopods. The sac is closed in the Bra- 
chiura and Schizopoda, but open in most Macrura. The otocysts of 
Crangon, Palemon, Hippolyte, Mysis, and Carcinus mzenas are described 
in more detail, but no good figures or sections are given. 

Auditory Hairs or bristles. Hensen gives the first and only good 
description of these. They differ from common tactile hairs in that the 
hair shaft is not directly connected with the wall of the sac, but a thin 
chitinous membrane intervenes, forming a small hollow sphere. It is 
this ‘‘ spherical membrane ” which allows the great freedom of move- 
ment necessary for the shaft in its response to sound vibrations. A 
peculiar process, the “lingula,” projects from the inner wall of the base 
of the shaft into the spherical membrane, and to this the nerve fibre is 
attached. The hair shaft is generally plumed, as in tactile hairs, with 
delicate chitinous filaments. 

In A. marinus the hairs are plumed and are nearly one millimetre in 
length. They are here very numerous, 468 having been counted in one 
case, and are arranged on the floor of the otocyst in four parallel semi- 
circular rows. 

A. fluviatalis has a much smaller number of hairs, but the same general 
arrangement ; Crangon, a row of only seven or eight ; these are more 
attenuate than in either of the above forms, but are 0.75 mm. in length. 

Palemon antennarius has about 40 hairs, arranged in a half-oval or 
horseshoe shape, the break in the oval being posterior. The hairs them- 
selves are peculiar in having their shafts bent at a sharp angle. The 
portion of the shaft above the bend is much longer and more attenuate 
than the basal part, and is also heavily plumed. These plumed ends 
project toward the centre of the horseshoe, and intertwine. Their length 
is about 100 u and their greatest diameter 3.84. The hairs of Hippolyte 
and Mysis strongly resemble those of Paleemon, but they are embedded 
in the single otolith and are therefore unplumed. 

Carcinus menas has about three hundred auditory hairs. They are 
grouped into three classes: — 1. Hook hairs (Hakenhaare): the shaft 
hooked and with a plumed tip, about thirty in number, 50 uw long, similar 
to the otolith hairs of Macrura. 2. Thread hairs (Fadenhaare) : long, 
filamentous, plumed at very tip, a single row of about 46, each 338 uw 
long, 3 in diameter. 3. Tuft hairs (Gruppenhaare): short, blunt, and 
unplumed, about 200 in number, occurring in a single large group. 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 17a 


Hensen also found on the appendages of some decapods free hairs 
which closely resembled auditory bristles, and are described as such by 
him. Crangon especially, which has few hairs in the otocyst, is supplied 
with many of these so-called “free auditory hairs.” They are also 
numerous in Mysis and Palzemon. 

Innervation of the Otocyst. In Palemon Hensen traced the nerve of 
the first antenna from the brain. A large branch of this nerve runs to 
the ventral side of the otocyst, where the fibres separate, each enlarging 
into a ganglionic cell and then proceeding to the base of a hair. Each 
of these terminal fibres (‘‘ Chorde ” according to Hensen) then enters 
the pore beneath a hair, passes through the spherical membrane to the 
lingula, or process from the base of the hair shaft, and makes itself fast 
to this. In his own words (Hensen, ’63, p. 368): ‘ Dieser eigenthiim- 
liche Faden, den wir als Chorda bezeichnen, lauft eine kiirzere oder 
lingere Strecke weit bis zu einem Hérhaare hinfort, und geht durch die 
Mitte des Porenkanals und der Haarkugel bis zur Lingula hin, an die er 
sich festsetzt.” Essentially the same conditions were found by Hensen 
in Carcinus menas and in Mysis. He also found nerve fibres supplying 
the tactile bristles which are present on all parts of the decapod body. 

Formation of New Hairs (Haarwechsel). New hairs are not formed 
inside the old, but beneath the chitinous wall ; and instead of developing 
from a single matrix cell, as was supposed, Hensen found that each was 
the product of a great number of cells. A new layer of chitin is 
formed beneath the old, and under this new layer, but continuous with 
it, the new hairs are formed as double-walled (i. e. invaginated) tubes. 
The new chitin wall is compared to the hand of a glove. If the 
fingers of the glove be turned partially outside in, so as to leave only 
their tips projecting, the condition would represent that of the hair 
tubes just. before the moulting of the old shell. The tips of the newly 
formed hairs become attached to the shaft of the old hair, into which 
they project some distance, and as the latter are detached at ecdysis, 
the new hairs are pulled out. Nerve fibres were found running into the 
very tips of the new hairs. Hensen’s theory is, that at moulting, the 
old nerve fibre, becoming more highly refractive and resembling chitin, 
is, upon the detachment of the old hair, drawn out through the apex of 
the new one, and that before this event a new fibre is formed. This 
theory, however, is not easily reconcilable with his statement that the 
nerve fibres attach themselves to the lingula at the base of the hair shaft. 

The remainder of this part of his paper is devoted to brief descriptions 
of the otocyst as found in some twenty-four different species of Crustacea. 


174 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


To this is added a table, embracing all the forms which have been stud- 
ied, giving the names of the different investigators, and the conditions, 
as to number and size, of both the auditory hairs proper (Otolithen- 
haare) and the “‘free auditory hairs” found on the antennz and abdomi- 
nal appendages. 

Lemoine (’68) compares the otocyst of the lobster with that of the 
crayfish. His descriptions are similar to those of Farre (43), but his 
figures are poor. The thin dorsal wall of the basal segment of the first 
antenna, which covers the ear sac, he calls the tympanic membrane of 
the lobster. The opening of the sac is overlooked, and the otocyst de- 
scribed as closed. Thus, as the otoliths cannot come from without, 
Lemoine’s theory is that they are exfoliations from the calcified walls of 
the sac, — an absurdly impossible assumption, as the thin chitinous walls 
of the otocyst are not calcified. In the case of the crayfish, he notes 
nothing new except that there is a membrane at the base of each hair 
shaft, separating its cavity from that of the spherical enlargement on 
which the shaft stands. This membrane acts as an ear drum, taking the 
place of the large tympanic membrane described for the lobster. 

Garbini (’80) discusses very briefly and incompletely the sense organs 
of Paleemonetes varians. The figures of the otocyst are extremely crude 
considering the date of the work, and simply confirm the conditions found 
by Hensen in Palemon. 

Vom Rath (’87, ’88, 91, 94) does not make the sharp distinction 
between auditory and tactile hairs that Hensen does, holding that the 
two kinds grade insensibly into each other, the auditory hairs being 
simply slightly modified tactile organs. All sensory bristles of Crustacea 
can be divided into two chief groups : — 

(1) Tactile or auditory hairs, with long, plumed shaft, the base of 
which is attached to the body wall by a delicate membrane of chitin, 
often spherical in form. Differentiation is thus towards freedom of 
movement in response to tactile or vibratile stimuli ; (2) taste or olfac- 
tory hairs, having a short blunt shaft, thick-walled at the base, but with 
either a small pore or thin permeable membrane at its distal end, by 
means of which chemical substances in solution can come into direct 
contact with the nerve endings. The nervous apparatus of these hairs 
is the same in both cases for all decapods. The sweeping statement is 
made, that beneath every sense hair there lies, either in the hypodermis, 
or removed some distance from it, a group of bipolar ganglion cells, From 
each of these cells a fibre is given off peripherally, and these, forming a 
strand, enter the base of the hair, ending only at its very tip. 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 175 


Claus (’75, 91) agrees with Vom Rath as to the nerve ending, but 
maintains that there is only one ganglion cell sending its process through 
a group of matrix cells into the hair. A misunderstanding as to the 
relations of the ganglion and matrix cells forms the basis of several con- 
troversial papers. 

Retzius (90, ’92, ’95) concludes in his last paper (95) that there may 
be several ganglion cells to a single sensory hair. The number may 
indeed vary from one to many. He was unable by any method to trace 
the peripheral nerve fibres further than the base of the hairs. Nerve 
endings, which he described in his first paper (90) as extending into the 
hair shaft, he afterwards (’92) frankly acknowledges to be artifacts. 

Bethe (’95*), in his admirable little paper on the otocysts of Mysis, 
clears up by modern methods many points, and corrects some of 
Hensen’s erroneous descriptions. The sac in Mysis is ellipsoidal, and 
pointed posteriorly, while from its floor rises a sensory cushion bearing 
the hairs. This cushion is tilted outwards and ventralwards 45°, the 
right and left cushions thus being perpendicular to each other. The sac 
is open, not closed as described by Hensen; the narrow aperture is con- 
cealed by the overlapping walls of the otocyst. Borne on the sensory 
hairs is the large otolith, oval as seen from above, kidney-shaped 
in side view; its greatest diameter 0.3 mm., the other dimensions 
being 0.25 mm. and 0.15 mm. It is composed of a more or less 
organic core, about which concentric layers of calcium fluoride are 
deposited. The tips of the sensory hairs are embedded in this inor- 
ganic layer, and penetrate to the core of the otolith. The layers of 
calcium fluoride are probably deposited from the sea water. The sixty 
sensory hairs are arranged in a single row, so as to form two thirds of 
a circle, the break in the line being posterior and toward the median 
plane of the animal. At one end of the curve five hairs are grouped 
together, and at the other end there is an irregular double row. 
Though much like the auditory hairs of Palemon, their tips, em- 
bedded in the otolith, are unplumed. Only one ganglion cell to a hair 
was found, sending a distal process into the base of each shaft. A 
double row of matrix cells lies just beneath the single row of hairs, 
and could easily be mistaken for ganglion cells. Vom Rath may have 
made this mistake, thus getting a multiganglion-celled condition for each 
hair. 

The otocyst begins to develop before the appendage is fully formed. 
An invagination of the dorsal ectoderm takes place, producing a shallow 
depression ; this enlarges while the opening gradually closes. Certain 


176 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


of the hypodermis cells elongate to form the matrix cells which later 
produce auditory hairs. The latter are formed only after hatching. 

Herrick (’95) mentions the auditory organ only in connection with 
the development of the lobster. The otocyst becomes prominent at 
the third larval stage, appearing as a shallow depression bordered with 
short setee and containing a few grains of sand. The depression gradu- 
ally enlarges, forming in the fifth stage a sac, the aperture of which 
decreases in size with successive moults, until the adult condition is 
attained. 

Bethe (95, ’97) has traced the auditory fibres of Carcinus menas 
centrally to the neuropil of the first antenna, where they end in 
delicate fibrillations. Some of these fibres may also end in the 
slobulus. 

From this review of the literature, it is seen that little has been done 
on the finer anatomy of the otocyst. Hensen’s work, once considered 
exhaustive, will not suffice at the present time. The organ of Brachyura 
has not been touched upon since Hensen’s dissections, while our knowl- 
edge as to the innervation of the different sensory hairs of Crustacea is 
left in a very hazy, confused state, since the exact condition of the 
peripheral endings is not firmly established, Claus, Vom Rath, Retzius, 
and Bethe each holding different views. The question remains un- 
settled as to whether the manner of innervation is the same for all 
the sensory hairs. G. H. Parker (’90) has clearly shown that the optic 
nerve in Crustacea is highly differentiated ; but all the other sense organs 
have, according to Vom Rath, the same manner of innervation, even 
though they differ in function as much as the so-called auditory and 
olfactory bristles. 

All the investigators of the crustacean otocyst, Bethe alone ex- 
cepted, carried on their work under the impression that they were 
dealing with an auditory organ. This certainly prejudiced them in 
drawing conclusions. But for this, Hensen would never have likened 
the thickened wall of the crab’s otocysts to the malleus of the verte- 
brate ear, nor made other far-fetched comparisons. A comparative 
study of the innervation of the otocyst, especially if supplemented 
by that of the olfactory and tactile bristles and the conditions in 
embryonic stages, cannot fail to clear up some of these questionable 
points. 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 177 


B. OBSERVATIONS. 


In the account of the morphology of the otocyst, two types will be 
taken for description : — 

(1) Open otocysts containing otoliths (macruran decapods); the 
example will be Palemonetes vulgaris Stimpson. The otocysts of 
the crayfish Cambarus affinis (Say) Girard, and of the prawn Crangon 
vulgaris Say, will be described in only sufficient detail to allow of 
comparison with Palemonetes, and to correct any errors or omissions 
in the descriptions of other investigators. 

(2) Closed otocysts without otoliths (brachyuran decapods) ; the sac 
_ of the green crab, Carcinus menas Lin., will be taken as the example 
of this type. 

For tracing out the development of the macruran otocyst (1), young 
lobsters were used instead of Palemonetes larve, as it is difficult to 
obtain a complete series of the latter, and their small size makes them 
by no means favorable material for studying the embryology of the 
sac. Young lobsters, however, can be had in abundance during the 
hatching season, and are of large size; the otocyst is of the same 
general type as that of Palemonetes. The development of the closed 
otocyst (2) was traced out in the crab for the sake of comparison with 
the macruran type of sac. 

The research represented in this paper was carried on at the sug- 
gestion of Dr. E. L. Mark, to whom I wish here to express my thanks 
for his constant kindness, suggestive direction, and able criticism. I 
am also indebted for valuable supervision and helpful suggestions to 
Dr. G. H. Parker, who directed my work for one year during the 
absence of Dr. Mark. 


1. Material. 


Large numbers of Palzmonetes were obtained from the Charles 
River, Cambridge, at low tide. These river animals live well in either 
salt or fresh water, and may be kept in aquaria without running water 
for an indefinite period. Being so hardy, and at the same time free 
swimmers, they are eminently adapted for intra vitam stains, and 
for physiological experimentation. 

Carcinus mznas was abundant in the soft-shelled condition, at Hadley 
Harbor, Naushon Id., during the months of June and July. The head 
of Great Harbor, Wood’s Hole, was another good collecting ground. 


178 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


Many soft-shelled animals were obtained by keeping young crabs in 
aquaria, and feeding them freely until ecdysis took place. 

Lobster larve were hatched at the U.S. Fish Commission Station, 
Wood’s Hole, during June and July. They were reared, but with 
great difficulty, up to the eighth moult. Fed on minced crab’s liver 
they throve well; but unfortunately they also fed indiscriminately on 
each other. 

Crangon was found in large numbers in the muddy bottom of the 
Charles River ; crayfish were bought in the New York City markets. 


2. Methods. 


In sectioning, great difficulty was experienced, both on account of 
the thickness of the chitin, which was often calcified, and because of 
the siliceous otoliths, so numerous in the sacs of Macrura, and glued by 
secretions to the hair tips. As the otoliths are insoluble in acids strong 
enough to completely destroy organic tissues, the only successful 
remedy was to remove them mechanically. This was best accomplished 
by washing them out by a stream of water blown into the sac. The 
apparatus for this consisted of a short piece of small rubber tubing into 
one end of which was inserted a glass tube drawn out to a fine point. 
The other end of the tubing being held in the mouth, and the capillary 
tube inserted into the aperture of the otocyst, a stream of water was 
driven into the cavity of the sac with considerable force. The larger 
otoliths having been washed out in this way, fairly good sections could 
be cut. 

In the crab, the difficulty in cutting the very thick calcified chitin 
was obviated by using soft-shelled animals. The chitin is at this stage 
very thin, uncalcified, and therefore more readily sectioned. Lobster 
and crayfish antennules were decalcified by placing them in Gilson’s 
fluid for twenty-four hours, or in Vom Rath’s platinic-osmic fixative 
for a week or ten days. 

Of the many fixing reagents used, (1) Vom Rath’s platinic-osmo-picro- 
acetic mixture, (2) his corrosive-picro-acetic fluid, and (3) corrosive 
sublimate plus 1 % acetic acid gave the best results and in the order named. 
The last two were followed by staining in iron haematoxylin, which 
gave a clear definite stain of sections as thick as 20u. The platinic- 
chloride fixative of Vom Rath was used for from three to five days, either 
followed or not by treatment with pyroligneous acid. In Palzmonetes 
and Crangon a fine differentiation of fibre tracts was obtained by using 


~ 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 179 


the fixative alone for three to five days, and washing out for at least two 
weeks in 90 % alcohol. The myelin sheath was intensely blackened, 
while all other tissues remained a yellowish brown. 

For tracing nerve fibres, both to peripheral and central endings, intra 
vitam staining proved of most value. Different methods were employed 
for obtaining peripheral and central stains. A one per cent solution of 
methylen blue in normal NaCl was injected into the body in either case. 

For peripheral endings several injections were made into the abdomi- 
nal blood space, at intervals of thirty minutes. When the animals 
showed signs of stupefaction, a final injection was introduced into 
the pericardial chamber. The amount of solution injected varied 
from a few drops, in Palemonetes, to five cubic centimetres, 
in the lobster. In from 15 to 30 minutes after the final injection 
the animals were usually dead. The part to be studied was then dis- 
sected out, barely covered with normal salt solution, and examined from 
time to time under the microscope, until a satisfactory degree of stain- 
ing had been reached. 

For central terminations one injection only was made, and this 
directly into the chamber of the heart, only a few drops of the solu- 
tion being required. When the blue color was well diffused throughout 
the tissues (about one hour after injection), the brain was dissected out, 
or exposed, and examined as before. For fixation of the stain Bethe’s 
ammonium-molybdate method for invertebrates was used. It was found 
to be better to leave preparations in xylol for only the shortest possible 
time, as this reagent diffuses the color. Preparations fixed by this 
method keep very well for a year or more, but after this they ultimately 
deteriorate, fibres originally sharp and continuous in outline becoming 
mere dotted lines, while the surrounding tissues take on a deep yellow 
hue. When both brain and otocyst were examined together, the peri- 
pheral cells and fibres stained first, then central fibres, central termina- 
tions, and ganglion cells of the brain in the order named. Sections 
60-120 uw in thickness were cut, but by far the greater number of pre- 
parations were examined in toto. The transparency of the tissues made 
this possible even with the brains, a millimetre or more in thickness, of 
large crayfish. 

To get constantly complete impregnations of both peripheral and cen- 
tral endings, it is necessary to expose to the atmosphere the part to 
be studied. The impregnation then takes place sooner, lasts longer, 
and affects a larger number of elements. The fixation of the color is 
also much better in this case, because the fluid can penetrate much more 


180 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


readily, and on the rapidity of its penetration depends, in a large meas- 
ure, the success of fixation. Gold-chloride and Golgi preparations were 
useful only for supplementing and controlling the results obtained by 
methylen blue. Both the rapid and slow processes for silver impregna- 
tions gave fairly good preparations, but by no means as complete or 
constant results as methylen blue. Ranvier’s gold-chloride method, 
in which formic acid is used for reduction, was very uncertain in its 
action on nervous tissue, but was quite useful in bringing out fine cell 
processes in the sensory hairs. 


3. Structure and Development. 
I. PALZMONETES VULGARIS STIMPSON. 


1. Structure of the Otocyst. 


a. Sac. This is situated, as in all decapods except the Myside, in 
the basal segment of the antennule, nearly filling its cavity. Its out- 
line as seen from above (Plate 1, Fig. 1) is nearly ovate, being well 
rounded posteriorly, though suddenly becoming pointed at its anterior 
end. In individuals of medium size (30 mm. long) its average dimen- 
sions are 0.66 mm. in length, 0.63 mm. in width, and 0.33 mm. in depth. 
In longitudinal section (Plate 1, Fig. 4) its outline is somewhat kidney- 
shaped, its length being about twice its depth, and its ventral wall 
projecting into the lumen. ‘Transverse sections through the basal 
portion of the antennule (Figs. 2, 3) show that the lumen of the otocyst 
is from one half to two thirds as wide as the antennule at this point. 
The chitinous wall of the sac, which is extremely thin, is continuous 
with that of the antennule (Fig. 3). The hypodermal cells form a 
single layer, except in the sensory region of the sac, where they are 
elongate and several layers thick. Median to the otocyst passes the 
antennular nerve, the cut end of which is shown at x. at. 1 (Plate1, 
Fig. 2), and directly below it lies the large muscle of the segment. 
Otoliths occupy the median and posterior portion of the lumen, and 
nearly conceal from view the sensory hairs (Fig. 3, set. ot.). In para- 
sagittal sections (Fig. 4) is to be noticed the close proximity of the 
brain (n’ pil. opt.), which is not more than 0.22 mm. posterior to the 
sac, and projects somewhat into the base of the antennule ; the sensory 
cushion, or prominence (crs. sns.), bearing the stumps of a few severed 
hairs, is also to be seen. 

The long axis of the otocyst is not coincident with that of the anten- 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 181 


nule (Fig. 1), as its anterior end is more lateral in position than the 
posterior. The external aperture has the form of a pointed ellipse and 
penetrates the dorsal wall of the antennule ; it is nearly as long as the 
sac itself, but does not extend quite as far back as the sac. It was 
described by some of the early writers as a longitudinal slit, by others as 
transverse; but, as Hensen points out, it is neither: its direction is 
oblique, and corresponds to that of the long axis of the otocyst. The 
opening is completely covered over by a thin fold of chitin (Figs. 1, 3, 
tet.), which extends forward and laterad to end in a sharp projection or 
spine. This lid-like fold (tectum) must be lifted or cut away in order to 
come directly at the opening of the otocyst. Figure 3 shows the position 
and form of the lid in transverse section, and how closely it fits over 
the aperture of the otocyst, while its forward projection over the an- 
terior lip of the slit can be seen in Figure 5 (Plate 2) at tet. As the 
chitinous lining of the otocyst is of ectodermal origin, like all other 
chitinous parts, it is cast off at each ecdysis, with all it contains, and a 
newly secreted sac takes its place. 


b. The sensory cushion of the otocyst is produced by an elevation of 
the median and posterior portion of the floor of the sac, which projects 
into the lumen and gives a somewhat constricted appearance to the cyst 
in sagittal sections. The surface of the cushion, which is about 0.25 mm. 
in diameter, is not horizontal, but slants downward from the median 
side of the sac to its lateral wall at an angle of nearly 45° (Plate 1, 
Fig. 3). This makes the sensory cushions of the right and left sides per- 
pendicular to each other, a condition similar to that described for Mysis 
by Bethe (’95*, p. 556), and of some physiological importance. The 
sensory hairs are borne on the sensory cushion, and for this reason 
the prominence has been compared to the créste acustice of vertebrates. 
The hairs, or bristles (for both names are applied to them), vary from 
forty-five to fifty-eight in number, and are arranged in a curved horse- 
shoe-like row (Plate 1, Fig. 1), the two ends of which are directed 
obliquely caudad and mediad. Largest at the inner end of the curve, 
and arranged in a single row, they grow gradually smaller toward 
the other end of the series, where an irregular double line is formed. 
Fig. 6 (Plate 2), a transverse section through the posterior ends of the 
horseshoe shows the base of a single hair on the right or median side, 
while at the left or lateral end two bristles are seen, the lateral row 
being double. 

Directly beneath the hairs we find, instead of the usual iayer of 

VOL. XXXVI.— NO. 7 2 


182 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


hypodermal cells, groups of cells with elongated nuclei; these send 
their processes into the bases of the bristles (Plate 2, Figs. 6,7). They 
are the matrix cells, which nourish the hair and, as we shall see later, 
have to do with its formation. The central region beneath the cushion 
is occupied posteriorly by the ganglion cells of the otocyst nerve (Plate 
2, Fig. 6, cl. gn.), and anteriorly by their peripheral fibres. 


c. Structure of hairs. The hairs of the otocyst are peculiarly modi- 
fied. Instead of being straight, as in tactile hairs, the shaft is here bent 
out of its course about 120°, so that its distal portion makes a sharp 
angle with the proximal end (Plate 2, Fig. 8). The shaft is very long 
in comparison with its diameter, being from 1604 to 200 u in length, 
while only 3 to 6 in diameter at the base. The part of it above the 
bend becomes extremely attenuate, and is heavily fringed with long deli- 
cate projections (pinnules), which give it the appearance of a plume. 
These fine feathery tips, which always project toward the concave side 
of the horseshoe formed by their bases, are crisscrossed and tangled to- 
gether in such a way as to form a wickerlike mesh, on which the majority 
of the otoliths rest (Plate 1, Fig. 3). The hairs are not attached firmly 
or immovably to the wall of the sensory cushion, but an exceedingly 
thin-walled chitinous bulb intervenes between the shaft and the wall of 
the sac. This, the spherical membrane of Hensen, is from 6 to 12 in 
diameter, and allows the shaft, itself comparatively rigid, to sway freely 
on its base, as if articulated there (Plate 2, Fig. 8, mb. sph.). 


d. The formation of hairs has already been described by Hensen 
(63, p. 374) in some detail. The conditions just before ecdysis were 
figured, but the earlier stages were not given; so a few supplementary 
facts may be added here.- Braun (’75) verified Hensen’s account of 
Haarwechsel in the bristles of Astacus, and himself discovered some 
new details. 

As before stated, each sensory hair is produced by a number of 
matrix cells, which send their processes into the shaft. In newly formed 
hairs, these protoplasmic processes extend to the very tip of the hair 
cavity (Plate 2, Fig. 7). In preparation for the next moult they are 
withdrawn nearly to the base of the hair, leeving the greater part of the 
hair cavity empty (Plate 2, Fig. 9). At the same time the matrix cells 
from which these processes are given off sink deeper into the tissue, below 
the level of the hypodermis, and with other chitinogenous cells originat- 
ing in the hypodermis, arrange themselves about the nerve fibre of the 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 183 


old bristle for the purpose of forming the new hair (Fig. 9, cl. ma.). 
This aggregation of cells is similar to the papilla described by Braun, 
but they are by no means as regular in outline and arrangement as 
those figured by him. In Palemonetes this condition of the matrix 
cells exists for several weeks before ecdysis takes place, the new hairs 
being formed during this period. In adult lobsters and crayfish the 
time is probably much longer, whereas in larve it lasts but a few days. 
The chitin of the new hair shaft is secreted part passu with that of the 
test, so that the two are continuous, but the hew hair is beneath the 
shell, in the region where the matrix cells have formed the papilla. It 
is secreted as a double tube, the distal end of the inner part of which 
projects, as the tip of the new hair, into the base of the old one. 
Figure 10 (Plate 3) shows the condition of affairs just before ecdysis in 
the endopod of the third abdominal appendage ; eta. being the old test, 
cta’. the new one formed beneath it. Three newly formed hairs are seen 
as double tubes located deep in the appendage. The walls of the two 
tubes are continuous with each other at their lower or proximal ends, 
and the tip of the inner tube projects distally into the shaft of the old 
hair. This inner tube, the tip of the new hair, must be secreted by the 
delicate processes from the matrix cells which still extend up into the 
old hair during the period of hair formation. The outer tube, though 
continuous at its lower end with the inner, is secreted by two parallel 
rows of matrix cells, very similar to the chitinogenous cells of the hypo- 
dermis, and probably derived from them. Hensen (’63, p. 375) has well 
described this condition of the new hairs as resembling that of the finger 
of a glove turned partially inside out, the tips alone projecting. The tip 
of the new hair is embedded in a viscous, homogeneous substance, which 
is formed between the old and the new tests, either by glandular secre- 
tion of other cells or by the chitinogenous cells themselves. This 
substance probably corresponds to the homogeneous non-cellular mem- 
brane found by Herrick between the shells of the lobster (’95, p. 87). 
When the old test is shed, it adheres to the fine plumes of the new hair 
tip, and aided by the internal blood pressure (very considerable at the 
moulting period), draws the recently formed hair out into its functional 
position, just as one would draw out the invaginated finger of a glove by 
pulling on its tip. The chitin of the shaft is very soft and pliable at 
this time, allowing the hairs to be turned right side out with ease; 
indeed, this may be done artificially. But if by some accident at the 
time of ecdysis any of the hairs are not at once fully drawn out, the 
chitin hardens and they are fixed in their abnormal position. 


184 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 


Aside from its general interest, this peculiar method of forming the 
new hair is very important, as throwing light on the peripheral endings 
of the nerve fibres in the sensory hairs. By it certain conditions may 
be explained. At each moult the nerve fibres lose their counection 
with the old hairs, and come into relation with new ones. How these 
changes are brought about can best be described in connection with the 
innervation of the otocyst. 


e. The Otoliths are borne in a rather compact mass upon the inter- 
laced tips of the sensory hairs (Plate 1, Fig. 3, ot’/th). They consist of 
irregular grains of sand mingled with other fine mineral particles and 
organic detritus. The largest measure from 8 to 12 uw in longest dimen- 
sion. That the greater part of them are siliceous is shown by their 
insolubility in strong sulphuric acid, and by the fact that they scratch 
glass when crushed upon it. They are renewed after each moult, 
for the freshly formed sac is at first without them. New otoliths are 
pushed in by means of the chele through the aperture of the sac 
while its walls are yet so soft and flexible as to admit quite large grains 
of sand. By watching animals soon after moulting it can be observed 
that they stir up the sand at the bottom of the aquarium in which they 
are confined ; as soon as some particles have come to rest upon the 
dorsal side of the antennule, one or both chele are raised, and by their 
tips the grains of sand are pushed back under the protecting lid of the 
opening into the otocyst. Otocysts from which most of the sand parti- 
cles had been carefully removed by forcing a jet of water into the sac 
were found after a lapse of two days to contain otoliths derived from 
iron filings which had been strewn on the bottom of the aquarium. The 
otoliths are often entangled in the feathery plumes of the auditory hairs, 
and are in this case attached to them by an organic substance, which is 
probably secreted by unicellular glands situated beneath the floor of the 
sac. No multicellular glands, such as are found in the lobster and cray- 
fish, could be detected beneath the otocyst of Palemonetes. Very 
minute canals, which are probably the ducts of gland cells, were found 
running through the chitin wall and some distance into the tissues | 
beneath ; they were very clearly brought out, and their tubular condi- 
tion proved beyond a doubt, in silver preparations, and in those made 
with lead formate; but unfortunately their connection with gland cells 
could not be demonstrated. The functions of the otolith and the 
part it plays in audition, or equilibration, will be discussed in the 
experimental portion of this paper. 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 185 


2. Innervation of the Otocyst. 


As already noted, the brain, or supra-wsophageal ganglion, is less 
than a quarter of a millimetre distant from the ear sac. The nerve 
supplying the hairs of the otocyst is thus comparatively short, and can 
be traced in a single section from the central to the sensory termination. 
Figures 4 and 12 (Plates 1, 3) show its general course after leaving the 
brain. Its sensory ganglion lies directly beneath the posterior end of the 
sac. The nuclei of the nerve cells of the ganglion are situated about 
0.25 mm. back of the hairs which they innervate, grouped irregularly 
together ; the peripheral fibres of the cells run somewhat parallel to one 
another, then spread out radially to the different hairs of the circle which 
they supply (Plate 3, Fig. 12, for. pi’ph.). 

There are three questionable points to be settled in regard to the 
innervation of the otocyst, and the same is true for the sensory bristles 
of decapod Crustacea in general. 

a. Is each hair supplied by one nerve fibre and sensory cell, or by 
many ? 

b. How do the peripheral fibres terminate? Do they attach them- 
selves to a sense cell, or to some part of the hair, or do they end free? 
If this latter be the condition, does the fibre terminate at the base of the 
hair, or at its very tip ? 

ec. Where do the fibres end in the central nerve organ, and how? 

For the determination of these questions, it is important to compare 
the conditions found in all kinds of sensory bristles. Because different 
types of hairs have been used in various Crustacea for the study of the 
nerve terminations, and this difference in kind of material employed by 
various investigators may account for the very diverse conclusions they 
have drawn. 

All sensory bristles of decapod Grubtepes can be divided into two 
general types : 

(1) Tactile bristles (Plate 2, Fig. 8) have typically a long, straight, 
plumed, attenuate shaft, attached at the base by a thin spherical en- 
largement, which allows great freedom of movement. 

Auditory hairs, so called, are merely modifications of these, for all 
gradations between the two exist. Tactile hairs are found on nearly all 
the appendages, and on some parts of the body. 

(2) Olfactory bristles (Plate 4, Fig. 13, set. olf., and Fig. 14) are short, 

cylindrical, or slightly tapering, and firmly attached as compared with 
tactile hairs, there being no marked basal enlargement. At the tip, the 


186 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


chitin is either pierced by a pore, or ends in a thin permeable membrane, 
which allows substances in solution to enter the cavity of the hair. If 
found on the first or second antennz, they are termed olfactory hairs ; 
when on the oral appendages, taste or gustatory bristles, though their 
functions are probably the same. 

a. Number of Nerve Elements to a Single Bristle. Until 1891 it was 
supposed that only a single ganglion cell and fibre-process supplied each 
bair. Then Vom Rath (91, p. 207) asserted, that beneath every sensory 
hair of crustaceans there is a large group of ganglion cells, each sending 
out a peripheral process, these converging and entering the base of the hair 
as a single large strand. ‘This opinion he again expressed in 1894 for 
all arthropods. He did not study the innervation of the otocyst, but 
apparently confined his attention to the olfactory type of hair, as his 
figures are all of unfringed bristles. 

The number of elements supplying each hair of the otocyst can be 
determined by, first, counting the number of fibres in the auditory nerve, 
and the number of nerve cells connected with these fibres, and then, 
secondly, comparing the statistics thus obtained with the number of 
hairs in the otocyst. If there is but a single cell and fibre toa hair, 
these numbers should coincide, at least approximately. But if there are 
always numerous elements, as Vom Rath maintains, then the number of 
fibres and nerve cells should be many times that of the hairs. The 
number of fibres can be readily.counted in a transverse section of the 
otocyst nerve stained intensely with iron hematoxylin and only slightly 
decolorized. The ganglion cells can be enumerated in serial sections cut 
in the plane of the long axes of the cells, so that their characteristic size 
and bipolar condition (seen in Plate 2, Fig. 6) will readily distinguish 
them from the hypodermal or matrix cells. From many such counts, 
the number of nerve elements was found to be approximately equal to 
that of the hairs. For example, in one otocyst there were 55 hairs, 53 
fibres in the nerve supplying them, and 58 cells connected with these. 
The number of cells could not be determined with perfect accuracy, as 
some cells may have been halved in sectioning. Slight variations in the 
numbers, however, are not of great significance, as, in order to have even 
two nerve elements to a hair, the number of fibres or cells must be at 
least twice as large as that of the hairs. Moreover, the ganglion cells 
are always isolated, and each is surrounded by a separate sheath ; their 
fibres are also separated from each other. Neither cells nor fibres occur 
in groups surrounded by a common sheath as Vom Rath (’92) describes 
them. In the otocyst, then, there is but one nerve element to each hair. 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 187 


In the tactile hairs the same methods of procedure were followed ; and 
further evidence was obtained from methylen-blue preparations. One 
of these is shown in Figure 11 (Plate 3). It will be observed at once 
from this figure that there is only one cell and one fibre to each hair. 
But in other preparations of the same appendage (Plate 4, Fig. 14) from 
two to ten cells are found grouped together irregularly, and sending all 
their processes to the same bristle. When this was the case, it was 
always observed, that the hair so supplied was of the short, blunt, fringeless 
type, and so possibly not a tactile but an olfactory hair. 

So far, the evidence has been entirely against Vom Rath’s statement ; 
but if we examine the innervation of the olfactory bristles, entirely differ- 
ent conditions will be found to exist, and in complete accord with his 
conclusions. 

On the inner flagellum of the first antenna of Palemonetes numerous 
olfactory bristles are found, arranged in rows of four or five hairs each 
(Plate 4, Fig. 13). The nerve cells and fibres supplying these hairs 
stain beautifully with methylen blue. Only single elements at first 
appear, but if the stain is allowed to act for a longer period, nearly every 
cell and fibre will become impregnated. It can then be seen that a large 
number of elements supply each hair. The cells are packed so closely 
together as to make the counting of a group difficult, but many counts 
upon sections stained in hematoxylin make it certain that more than a 
hundred cells may compose a single group, and supply a single olfactory 
hair. The cells send off each a peripheral fibre. These fibres enter the 
base of an olfactory hair as a single large strand, 12 to 15 w in diameter. 
In Figure 13 only a few of the elements are shown ; the sheath, which 
surrounds both cells and fibres, marks the outline of the spindle-shaped 
group of cells, and shows the size of the fibre strand. 

The gustatory hairs on the oral appendages are also each supplied 
with numerous nerve elements (Plate 4, Fig. 14). The number is 
not nearly so great as in the olfactory hairs, —averaging about 10 to 
a hair, —nor are they so regularly and compactly grouped, They differ 
markedly, however, from the conditions found in tactile and otocyst 
hairs. 

The distinctly different conditions —as regards the number of nerve 
elements of the hairs— found in the olfactory and otocyst bristles, seem 
to explain the diverse conclusions of Bethe and Retzius on the one hand, 
and Vom Rath on the other. The two former observers worked on the 
tactile type of sensory bristles, while Vom Rath, as his figures show, 
evidently confined his attention to the other type. The conditions which 


188 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


Vom Rath found in the olfactory type he too hastily attributed to all 
the sensory hairs of Crustacea, 

b. Peripheral Terminations. Here again we find a difference of opin- 
ion. Hensen (63, p. 368) asserted that the peripheral fibre was 
attached to a process (ingula) from the base of the hair shaft. Claus 
(91), Vom Rath (92, ’94), and Bethe (’95) found fibres reaching to the 
very tip of the sensory bristles; while Retzius (’95, p. 17) found no 
evidence of nerve terminations beyond the enlargement at the base of 
the hair in decapods, though he observed in Hntomostraca the same con- 
ditions as did the other three investigators. 

I have obtained hundreds of preparations of nerve endings in the 
various sensory hairs of Palemonetes with several of the best modern 
nerve methods, and all furnished the same evidence. The conditions 
found for otocyst hairs were in every case as illustrated in Figures 4 
and 8 (Plates 1, 2). The ganglion cells, as already noted, lie at some 
distance (0.25 to 0.40 mm.) from the bases of the hairs which they supply. 
The reason for this becomes obvious, when the formation of the new 
hairs is considered. The developing hair tube extends below the base of 
the old hair a distance equal to at least one-third the length of the hair, 
and the ganglion cells necessarily lie below the lower or proximal end 
of the hair tube (Plate 3, Fig. 10, tb. set.). Hence they must be at least 
a third the length of the hair distant from its base, though they occupy 
a closer position directly after ecdysis than for some time before. The 
terminal fibres (Plate 2, Fig. 8, fbr. n.), which are as long as the dis- 
tance of their cells from the hairs, enlarge slightly as they near their 
termination, and always end in the expanded base of the hair directly 
below the shaft proper. There are no signs of attachment to any part 
of the wall of the hair, nor of fine branching of the distal end of the fibre, 
such as Retzius (’90) describes. Figure 4 (Plate 1) shows diagram- 
matically one nerve element of the otocyst, the position of the ganglion 
cell, and the ending of its peripheral fibre in the base of the hair. In 
Figure 8 (Plate 2) only the termination of the fibre, highly magnified, 
is given. 

The elements of the tactile hairs end in precisely the same manner as 
those of the otocyst. A number of these endings are shown in Figure 
11 (Plate 3). In no case was a nerve ending demonstrated in the shaft 
of the hair. Thus, all the evidence of preparations goes to prove that 
in both otocyst hairs and tactile hairs the nerve fibre, without branching, 
ends in the enlargement at the base of the hair, and never enters the shaft 


itself. 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 189 


In the olfactory bristles the cells are situated about 0.40 mm. posterior 
to the bases of the hairs, and their peripheral nerve fibres, stained by 
methyien blue, were traced tn almost every preparation, some distance 
into the shafts, though in the tactile hairs of tie same appendage no fibres 
could be followed further than the base. Figure 13 (Plate 4) shows 
the olfactory endings, some of them extending half the length of the 
hair shaft, but none as far as the tip; nor was such a condition ever 
found, although a great number of preparations were examined. The 
direct evidence of preparations shows, then, that the peripheral nerve 
endings are different for the different types of hairs. The fibres terminate 
in the enlarged base of tactile bristles, while in olfactory hairs they end 
Sree in the shaft itself. 

This direct evidence is strengthened by other structural conditions. 

(1) Owing to the rigidity of the hair shaft and its delicate basal 
attachment, a mechanical stimulus applied to a tactile hair would be 
apt to proluce its strongest effect at the base. Therefore we should 
expect to find the nerve termination at this, the point of greatest stimu- 
lation. The innervation of the tactile hairs of vertebrates extends only 
to the base, yet the slightest touch of the hair tip stimulates the nerve 
ending. 

Similarly, in the otocyst hairs the point of greatest stimulation must 
be at the base. The hair tips are so entangled with each other, and with 
the otoliths resting upon them, that a stimulus applied to one must 
affect them all. If this stimulus is caused by the shifting of the weight 
of the otoliths resulting from a change in the direction of the pull of 
gravity, it will affect the delicate, labile articular membrane at the base 
of the hairs far more vigorously than the part of the shaft attached 
to an otolith, or entangled with the tip of another hair which is so 
attached. i 

In the olfactory hair, on the other hand, the chemical stimulus finds 
access through the permeable tip, and, traversing the cavity of the shaft, 
comes at once into contact with the terminations of the nerve, which 
here, as we have seen, runs some distance toward the tip of the hair. 
This, then, is a condition of affairs which, in view of the function of the 
olfactory hairs, we should reasonably expect. 

(2) The conditions during hair formation are very unfavorable to the 
assumption that the nerve fibres extend to the tips of the tactile and 
auditory hairs. In adult Palemonetes, a month at least before ecdysis 
takes place, the matrix cells withdraw their processes to the basal por- 
tion of the hair, leaving the upper part of the shaft empty. As the 


190 - BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


shrimp moults once in two or three months, this means that for nearly 
half the time the nerve fibre canuot extend further than the base of the 
hair. Yet the animals are apparently as sensitive to stimuli during this 
period as at any other. After the new hair is fully formed, and its tip 
projects into the base of the ojd hair, which has now lost all direct 
nerve connection, the animals still respond quickly to tactile stimulus ; 
the impulse resulting from the stimulus is transmitted from the tip of 
the old hair to its base, thence to the shaft of the new hair, by which 
in turn it is transferred to the nerve fibre. 

(3) If certain of the nerve fibres supplying the tactile hairs are 
stained with methylen blue just before ecdysis when the new hairs are 
fully formed but still deeply invaginated (Plate 3, Fig. 10, 7. set.), 
they may be traced some distance into the shaft of the xew hair. Now, 
by removing with a fine needle the old test, cta., the new hairs can be 
pulled out into their functional position. The nerve fibres, however, are 
not pulled out with the hair the whole distance, but remain nearly in 
their original relative positions, barely projecting into the bases of the 
hairs, a condition already pointed out in Figure 11 (Plate 3). 

It is unfortunate that the investigators of these nerve endings have 
never taken into account the tissue changes — certainly of great impor- 
tance — which occur in all Crustacea between moults. 

At certain stages in their formation the delicate protoplasmic pro- 
cesses in the tips of the new hairs stain very sharply, and have a 
varicose appearance, similar to that of nerve fibres; as these project 
some distance into the old hairs, they might easily be mistaken for 
terminal nerve endings. 


ce. Central Terminations. By means of methylen-blue preparations the 
nerve fibres supplying the otocyst were traced continuously in their course 
from the sac to their central endings. Whole preparations of the anten- 
nules and brain could be used for this purpose, as the tissues were ex- 
tremely transparent. On account of the proximity of brain and otocyst, 
the nerve supplying the latter is very short. It enters the anterior end 
of the brain lateral to the antennular nerve, the two joining as they 
pass within (Plate 3, Fig. 12). While the antennular nerve pursues 
a straight course, the other (Figs. 2, 4) descends from the sensory hairs 
in the floor of the otocyst, forms the sensory ganglion, and in continuing 
its course approaches somewhat the median plane and describes the 
form of an elongated letter S, the plane of which is dorso-ventral. 
Just before the two nerves unite to enter the brain, a third smaller 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 191 


nerve is received by the otocyst nerve on its dorsal side (Plate 1, 
Fig. 2, rm. /.). This nerve is formed by an aggregation of fibres from 
the tactile bristles of this segment of the anteunule, and runs almost 
straight toward the median plane till it joins the nerve of the otocyst. 
The fibres of the latter enter the anterior end of the brain ventral to 
the optic neuropil, and median to the’ globulus (Plates 1, 3, Figs. 
4, 12); they extend backward to near the posterior end of the central 
organ in an almost horizontal plane, lateral to the fibres of the antennular 
nerve. They end in a region just anterior and median to the neuropils 
of the second antenne, branching into delicate dendritic fibrille, which 
form a well-marked neuropilar mass (Fig. 12, for’.). 

Fibres supplying the tactile hairs of the basal segment of the anten- 
nule end in the same neuropil, while the main nerve to the antennule 
ends in a closely connected fibrillar mass just median to it. No nerve 
cells were found in the brain connected with the sensory fibres from the 
otocyst. Association elements, with large dendritic branches, put these 
newropils into communication with the optic centres. One of these con- 
necting fibres is shown in Figure 12 (for. ass.). Its cell, which sup- 
posably exists, was not stained. According to Bethe’s (’97, Taf. xxviii. 
an.1) experimental work on the brain of Carcinus menas some of the 
otocyst fibres should end in the globuli. He could not demonstrate 
such fibres, however, in his preparations of the erab’s brain, nor was I 
able to obtain conclusive evidence of such endings in the globuli of 
Palzemonetes. 


d. Histology of the Nerve Elements. The nerve fibres of Pale- 
monetes are relatively large ; those of the otocyst reach their greatest 
size immediately before they enter the neuropil substance of the brain. 
At that point in their course they are from 3 to 5p in diameter, not 
including the nerve sheath. In a transverse section of the nerve the sep- 
arate fibres show distinctly, as they are held apart by connective tissue. 

The fibrillar structure was made out definitely only in methylen-blue 
preparations which had been well differentiated in process of fixation. 
The gold-chloride method of Apathy, though tried several times, did 
not give a successful reaction. Fibrille were made out distinctly in 
only one preparation, though some evidences of such structure appeared 
in many. Figure 15 (Plate 4) shows a portion of a peripheral fibre in 
which many fibrils are seen ranning longitudinally. No single fibril 
was traced any considerable distance, nor could any evidence of the 
fibrils be found in the ganglion cells. The fibrille are embedded in a 


192 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


semi-fluid, homogeneous substance, which is the first to take up the 
methylen-blue stain. It has been called by Bethe (98) the “ peri- 
fibrillar substance.” The accumulation of this fluid into drops gives 
the characteristic beaded appearance of methylen-blue preparations. 

A distinct nucleated myelin sheath surrounds both the fibre and the 
peripheral ganglion cells of Pulemonetes. This sheath, which stains 
intensely black in Vom Rath’s platino-osmic fixative, can be traced 
some distance beyond the peripheral ganglion cells toward the sensory 
hairs, and also centrally into the brain, where it ceases only when 
the fibres enter the neuropil substance. Figure 16 (Plate 4) shows 
a ganglion cell and its peripheral process surrounded by the sheath. 
Elongated, flattened nuclei occur at intervals along the walls of the 
sheath, curved around it and the enclosed fibre; certain of these 
sheath nuclei can be seen in Figure 4 (nl. tu.) between the ganglionic 
cells and the brain, though the myelin sheaths are not stained in this 
hematoxylin preparation. Quite frequently one of them may occur 
in close proximity to a ganglion cell. Thus are produced (Plate 4, 
Fig. 17) appearances which might be mistaken for a ganglion cell with 
two nuclei. Careful study, however, shows that one nucleus (l.) lies 
within the cell, the other (nl. tu.) without, but abutting on the 
ganglion cell so closely as to sometimes change its form. In every 
instance of this kind one of the nuclei, owing to its irregular outline, 
its smaller size, and the curved form which it takes in adaptation to 
the surface of the cell, could be identified as belonging to the sheath 
rather than to the nerve cell. 

The peripheral ganglion cells are much elongated and are of the 
typical bipolar form (Plate 4, Fig. 18). They measure from 10 to 
14, in diameter; their nuclei are relatively large, measuring from 
7 to 9 in diameter, and are usually ovate in outline, their length in 
some cases being twice as great as their diameter. One large spherical 
nucleolus ig usually present in the chromatic network, though some- 
times two or more are found. No definite structure can be recognized 
in the cytoplasm of the cell, nor any traces of fibrillee; this, however, 
is not strange, as the cell usually stains so intensely that it would not 
be reasonable to expect to make out its finer structure. In methylen- 
blue preparations a narrow zone about the nucleus stains only faintly, 
the coloration becoming more intense as the periphery of the cell is 
approached ; so here, as Bethe also found in the nerve cells of Carcinas, 
the chromatin granules are more numerous at the periphery of the cell 
cytoplasm, and nearly wanting around the nucleus. 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 193 


3. Development of the Otocyst (in Homarus americanus Milne-Edwards). 


In order that the development of the otocyst in the lobster may be 
more readily understood, it may be best to compare briefly its adult 
condition with that of Palzmonetes. 

It was dissected and described by Farre (43), and again by Hensen 
(63). The sac is drawn out posteriorly into a dorso-ventrally flattened 
projection, the “cochlea” of Hensen. The external aperture is extremely 
small, guarded by bristles, and located at the median, dorsal, and ante- 
rior end of the sac, the dorsal wall of which, like the dorsal wall of 
the antennule, is very thin, forming the so-called tympanic membrane. 
On the floor, which is nearly horizontal, there is a semi-circular ridge 
(Plate 5, Figs. 24, 26), which forms the sensory cushion. From this 
arise the otolith hairs, which have straight shafts, and number from 
500 to 600. The four rows of these are so arranged as to form a semi- 
circle, the open side of which (at the right in Plate 5, Fig. 26), is ante- 
rior instead of posterior as in Palemonetes. At the anterior end of the 
curve there is an irregular group of smaller hairs, with bent shafts. On 
the median wall of the sac, near its posterior end, there is an irregular 
double row of long thread-like hairs, with shafts heavily fringed (Fig. 
26, set. m.). The otoliths are numerous, and rest on the area surrounded 
by the rows of sensory hairs, and also on the hairs themselves; the 
thread-like hairs are free, and float out into the lumen of the sac. 

Not much has been written on the development of the otocyst in 
decapods. Reichenbach (86), in his work on the embryology of the 
crayfish, figures the invagination of the “auditory sac” at an early 
stage in the egg. The crayfish, however, as it develops into the adult 
form without passing through the larval stages characteristic of most 
other decapods, is not a typical example. Herrick (’95, p. 194) alludes 
to the appearance of the otocyst cavity in the third larval stage of 
Homarus, and he shows its position at this stage in connection with the 
development of the first antenna. In the fourth stage it is a shallow 
depression containing a few otoliths and in the fifth larva its aperture 
begins to close. 


I shall describe its condition in the first four larval stages. 


a. First Larval Stage. 


(Schizopod larva, without abdominal appendages. ) 
Sections of lobster eggs in different stages up to time of hatching 
showed no evidence of the otocyst in the antennule, and it became 


194 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


apparent that its development took place wholly in the free-swimming 
stages. A transverse section through the antennule of a newly hatched 
larva (Plate 4, Fig. 19) shows no sign of invagination in the region 
where the sac is to appear. But certain elongated nuclei, evidently 
those of modified hypodermal cells, are found grouped, two or three 
layers deep, beneath the dorso-lateral wall of the appendage (Fig. 19, 
cl. ma.). These elongated nuclei, viewed from the dorsal surface of the 
appendage, are seen to be roughly arranged in a semi-circle, like the rows 
of otocyst hairs in Figure 26 (Plate 5), and when traced through later 
stages, the position they occupy is found to be directly beneath the ridge 
where the sensory hairs later appear (Plate 5, Fig. 24, set. of.). They 
are evidently, therefore, the nuclei of the matrix cells which build up 
by secretion the chitinous walls of the sensory hairs. These cells, like 
those which take part in hair formation after ecdysis, originate from the 
-chitinogenous hypodermal cells by simply becoming elongated and sink- 
ing beneath them. A similar arrangement of matrix cells was found in 
the developing otocyst of Mysis by Bethe (95*). Numerous spherical 
nuclei, which stain in a manner characteristic of nerve cells, are present 
just below the matrix cells (Fig. 19, n’bl.). . If traced back to the gan- 
glionic masses of the brain, they are found to be continuous with the 
nerve cells of the latter, and probably originate from them. 


b. Second Larval Stage. 


(Second to fifth pair of abdominal appendages present.) 

In this larva the first evidence of invagination is seen on the dorsal 
side at the base of the antennule (Plate 4, Fig. 20). The nuclei of the 
matrix cells are now larger, and very conspicuous at the lateral side of 
the transverse section, the region where the rows of hairs will later 
appear. Figure 22 (Plate 4) shows the anterior and posterior limits of 
the invagination and the fundament of the sensory ridge, marked by a 
fold in the hypodermis and chitin at el. ma. The matrix cells just 
posterior to this fold, whose processes are directed toward it, are those 
which are to form the transverse portion of the hair rows. As in the 
first stage, nuclei of nerve cells lie immediately beneath the matrix cells, 
but the cytoplasm about them shows as yet no definite boundaries or 
outlines, nor are there any signs of nerve fibres connected with them. 


e. Third Larval Stage. 


(Chele relatively larger, uropods present.) 
In this stage (Plates 4, 5, Figs. 21, 23) invagination has proceeded 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 195 


still further. There is a deep lateral, as well as a posterior, fold in the 
chitin ; but the sac, if it can now be called such, is very shallow, wide- 
mouthed, and without sensory hairs or otoliths, From the group of 
matrix cells, however, the tips of embryonic sensory hairs may be made 
out, projecting dorsally, but covered by the chitinous floor of the sac 
(Plate 5, Fig. 27). Only after the wall of the sac has been shed at the 
next moult will they become functional organs. 


d. Fourth Larval Stage. 


(Form like that of adult ; thoracic exopods rudimentary.) 

The sac has now greatly increased in size, and nearly fills the cavity 
of the appendage (Figs. 24, 25). Its opening has become smaller, 
and is protected by numerous fringed bristles, which project from its 
sides (Fig. 25, tct.). About 200 sensory hairs are present borne on a 
prominent sensory ridge (Fig. 24, set. ot.) and arranged in three regular 
rows, one row less than in the adult stage (Fig. 26). The whole band 
bears some resemblance to a sickle. Beginning at the median side of the 
sac floor, the rows curving only slightly run laterally, then with a 
stronger bend turn forward. At the anterior end of the sac regular 
arrangement ceases, the hairs being grouped promiscnously. Besides 
these large hairs on the sensory ridge, which measure 120 uw to 150 uw in 
length and from 4 u to 6 uw in diameter, there is, as in adults, an irregular 
row of more attenuate hairs arranged longitudinally along the posterior 
part of the median wall (set. m., Fig. 26). They number about thirty, 
are on the average 140 w in length, and have a diameter of only 2 to 3 u 
at the base of the shaft. 

Many otoliths, consisting of fine particles of sand, rest on the hairs of 
the sensory ridge, as in the adult condition, but do not come into con- 
tact with the attenuate bristles of the median side-wall, which project 
free into the liquid contents of the otocyst. The sensory ridge is much 
more prominent at this stage than in the adult. This, and the size of 
the aperture, are the chief differences between the two, and are well shown 
in Figure 25. The opening gradually becomes smaller in the fifth, sixth, 
and seventh stages, until in the full-grown animal it is almost obliterated. 
A fourth row of hairs, not yet developed, is formed posterior to the 
others at some stage later than the seventh moult, this being the oldest 
stage that I have studied. Except for the gradual closure of the aper- 
ture, the larvee of the fifth, sixth, and seventh stages show the same 
conditions in the otocyst as the stage under consideration. 

In Figure 24 (Plate 5) ganglion cells (el. gn.) are seen beneath the 


196 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


sensory ridge. The origin of these could not with certainty be traced 
out in the material at command, though from the conditions found in 
the first stage, it is probable that they are derived from the neuroblast 
cells of the brain. ‘The only evidence in favor of this view is the prox- 
imity of the brain, and the fact that at an early stage nerve cells which 
were continuous with the ganglionic masses of the brain were present 
beneath the matrix cells of the otocyst. Figure 26 shows, somewhat 
diagrammatically, the general innervation of the otocyst hairs of the 
fourth larval stage, as brought out by methylen blue. The condition is 
essentially that of the adult. There is but one nerve element to each 
hair, and the endings are in the enlarged bases. No myelin sheath is 
developed in either the larva or adult lobster. Central terminations of 
the otocyst fibres were not traced out, nor was their finer histology 
investigated. 

The most striking point to be noted in the development of the otocyst 
of the lobster is the abrupt change which takes place after the third 
moult. The shallow, functionless depression of the third stage is con- 
verted at once into the active, well-differentiated organ of the fourth 
larva. This sudden leap in the development of the otocyst is correlated 
with an abrupt metamorphosis of the larva’s general form and method 
of locomotion. As this correlation may have an important physiological 
significance, it will be discussed in detail in the theoretical portion of 
this paper. 


II. CRANGON VULGARIS Say. 


1. Structure of the Otocyst. 


a. Sac. The otocyst has been described only briefly by Hensen (’63). 
He figures the sac dissected out, and gives two sketches of the sensory 
hairs, and the prominence upon which they are borne. 

The sac, as seen in a section passing through its middle and trans- 
verse to the long axis of the antennule, has the form of a half-circle. In 
a cross-section more posterior its outline is made irregular by the pro- 
jection of the sensory ridge or cushion from its lateral wall (Plate 6, Fig. 
28). This is an entirely different condition from that found in Palz- 
monetes, where the sensory cushion is basal. More irregular still is its 
form in frontal section, as shown at ers. sns. in Figure 29 (Plate 6). The 
dimensions of the sac in individuals of medium size (25 mm. long) are : 

length 0.44 to 0.55 mm. 
width 0.28 “0.38 ‘ (anterior to sensory ridge) 
depth 0.20 “0.22 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 197 


It is thus relatively wider, and more shallow than that of Paleemonetes. 
The wall is of thin chitin continuous at the large oval aperture (Plate 7, 
Fig. 30) with that of the dorsal side of the antennule. The aperture is 
as wide and nearly as long as the sac itself; instead of a fold of chitin 
it has for protection a row of large fringed bristles. These are ranged 
close together along the posterior edge of the opening and extend their 
long parallel shafts beyond its anterior margin. A fine-meshed grating 
is thus formed, through which even microscopic organisms could not pass 
without displacement of the bristles. 

b. The sensory cushion (Plate 6, Fig. 29, ers. sns.), as already noted, 
projects from the posterior portion of the lateral wall of the sac. Its 
direction is not transverse to the long axis of the sac, but it points 
obliquely forward and mediad. It is a ridge rather than a cushion, for 
the hairs are arranged in a short, nearly straight single row, instead of 
in several rows having the form of a sickle. This row of hairs, which 
defines the limits of the sensory region, starting at the dorsal end of the 
ridge, takes a course along its convex surface downward and backward, 
and ends where the ridge disappears, just before the floor of the sac is 
reached. A portion of a row of hairs is shown in the right otocyst, 
Figure 29, set. ot. (Plate 6), where the hairs anterior in position are really 
above or dorsal to those posterior to them. ‘The ridge-like projection of 
the sensory prominence is best seen in a parasagittal section (Plate 7, 
Fig. 30, set. ot.), a hair being there shown at the apex of the ridge. 

The matrix cells are essentially the same as in the hairs of 
Paleemonetes. They occupy the region just beneath the bristles, into 
which their processes extend. The space in the sensory prominence 
below and lateral to the matrix cells is occupied by the sensory ganglion 
cells, the fibres from which penetrate between the formative cells and 
reach the bases of the hairs (Fig. 29, el. gn). 

c. Structure of hairs. Arranged on the sensory ridge in the manner 
above described, the hairs of the otocyst are 26 in number, as shown by 
the average of a large number of individuals. They are largest at the 
upper anterior end of the row, where they measure 180 w in length and 
about 9 in diameter at the base of the shaft. Proceeding down the 
line they are successively smaller, the last of the series being only 100 u 
in length and 6 in diameter. There is a conspicuous spherical enlarge- 
ment at the base of the hair shaft (Plate 7, Fig. 31, mb. sph.), as in the 
otocyst hairs of Palemonetes. The shaft itself for about a third of its 
length projects straight out horizontally into the lumen of the sac. 
Then it bends down ventrally nearly at right angles, though the amount 

VOL. XXXVI.— NO. 7 8 


198 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


of curvature is different for different hairs. The larger, being in a mcre 
elevated position, usually bend at a sharper angle than those near the 
floor of the sac. All are heavily plumed ; the pinnules are long and 
coarse (Plate 7, Fig. 31, pinn.) and often have otoliths firmly attached 
to them by a substance probably of glandular origin. Hensen (63) 
describes the otolith hairs of Crangon, as follows: ‘Es steht nimlich auf 
die schon erwihnten Vorbuchtung eine einzige Reihe von 7 oder 8 
Haaren ; diese Haare reichen bis zur Kugel in die Steine hinein, thre 
Zahl erscheint viel zu gering fir deren Masse. . . . Sie sind 0.075 mm. 
lang, 0.0075 mm. breit und gerade anfgerichtet.” 

This description of these hairs is completely at variance with the 
conditions I have found in the American Crangon. In order to deter- 
mine, therefore, whether this was a true specific difference, or due to an 
error on Hensen’s part, a number of the European specimens, procured 
by Dr. Mark from Professor Herdman in Liverpool, were examined. 
After dissecting out the otocysts of 12 specimens, I was entirely satisfied 
that Hensen’s description was incorrect. The hairs are precisely the 
same in size, form, and number as in the American variety. They have 
their shafts distinctly bent near the tip at angles varying from 25° to 90° ; 
of the individuals examined none possessed less than twenty-four hairs 
in the sac, the average being twenty-six. 

That Hensen should have made such a mistake is not strange. He 
himself says: “their number appears much too small for the mass [of 
the otoliths].” The tips of the hairs are concealed by the otoliths, and 
only the first third of the row would be visible from above. 

d. The formation of hairs after ecdysis is identical with that of 
Palzemonetes. 

e. The otoliths are numerous, larger than in Paleemonetes, and found 
mostly in the posterior part of the sac, in contact with, or even attached 
to, the fringed tips of the hairs. Mainly siliceous, they are taken in 
after each moult, being readily pushed into the large opening of the 
otocyst. They can be almost completely washed out by a fine jet 
of water introduced artificially, and if the animal so treated is then 
placed in an aquarium containing iron filings, or other substitute, this 
material will soon be used to replace the otoliths of sand. 


2. Innervation of the Otocyst. 


As in Paleemonetes, the brain is very close to the otocyst, and the 
nerve supplying the sac is therefore short. Its general course is shown 
at n. ot. in Figure 29 (Plate 6). 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 199 


Leaving the anterior end of the brain with a bend away from the 
median plane, it gives off in front of the globulus a small lateral branch 
(rm. l.), which supplies the tactile bristles of the antennule. The main 
nerve, after passing between the globulus and the posterior end of the 
sac, runs forward only a short distance to the sensory prominence on the 
lateral side of which its ganglion lies. The peripheral fibres can be 
traced forward and slightly mediad from the ganglion to the bases of the 
otocyst hairs. The whole course of the nerve is approximately in a 
frontal plane, though its peripheral ending is slightly more ventral than 
its point of departure from the central organ. In Figure 28 (Plate 6) the 
transverse section of the antennular nerve (x. at.) is seen to be median 
to the sac, while the ganglion cells of the otocyst nerve (cl. gn.) are 
lateral to it. 

a. Number of Nerve Elements to a Single Bristle. There is in Crangon 
but one ganglion cell and fibre to each otocyst hair. The cells and fibres 
were counted as in Palemonetes, and the numbers thus obtained were 
found to agree approximately with the number of the hairs. 

Methylen-blue preparations of the olfactory nerve elements were 
obtained, and the conditions there brought out agreed essentially with 
those found in the same type of hair in Palzmonetes, large groups 
of nerve cells being present beneath each olfactory bristle. 

b. Peripheral Terminations. Nerve fibres to otocyst hairs were 
never traced beyond the enlarged base of the bristle, where they end free 
without branching. A typical nerve element of the otocyst is given 
diagrammatically in Figure 29; it shows the peripheral ending of the 
fibre at the base of set. ot. 

In the olfactory hairs, on the other hand, the nerve fibres in most 
cases could be traced up into the shaft of the hair, though never through 
its whole length. Thus in Crangon, as in Palemonetes, there is a 
distinct difference in the innervation of the two types of bristles, both as 
to the number of elements, and in the manner in which the fibres end. 

c. Central Terminations. Centrally the otocyst nerve ends in a posi- 
tion (Fig. 29) corresponding to that of the central terminations in Pal- 
emonetes, but the fine fibrillar branching, which was brought out 
distinctly by methylen blue in that form, could not be impregnated in 
Crangon. 

d. Histology of the Nerve Elements. So far as worked out, this was 
similar to that already described in Palemonetes. A myelin sheath is 
present in Crangon as well as Paleemonetes, though it was not observed 
in any other decapods. 


200 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


3. Development of the Otocyst. 


This was not studied in Crangon. 


II]. CamBaRUS AFFINIS (Say) GIRARD. 


The otocyst of the crayfish has been figured by only Farre (’43) and 
Huxley (80). The description of the former investigator was excellent 
for the time at which it was made. Huxley alludes to the otocyst in 
his work on the crayfish, and gives one figure showing the sensory 
region dissected out. Hensen (’63) describes the hairs of the otocyst 
in Astacus fluviatalis, but does not touch upon its other structures. 


1. Structure of the Otocyst. 


a, Sac. The otocyst of Cambarus (Plate 8, Figs. 37, 38), except for 
its smaller size, resembles that of the lobster very closely. The aper- 
ture, exceedingly small in the lobster, is here quite large, though, on 
account of the dense chevaux de frise of fringed bristles, it seems smaller 
than it really is. These bristles, projecting from around its margin, 
effectually cover and conceal the opening. It occupies the middle of the 
dorsal side of the antennule; its anterior margin corresponds to the 
anterior wall of the otocyst, and it extends back from this point nearly 
one-half the length of the sac. Its width is about one-third that of the 
otocyst (Fig. 37). 

The cyst does not by any means fill the cavity of the antennule. It 
is rounded off in front, but sharply pointed at its posterior end, where 
it is very shallow (Fig. 38). Its walls are of uncalcified chitin and 
continuous with the very thick calcified shell of the antennule (Figs. 37, 
38). Its dimensions in average-sized animals are: 

Length from 1.75 mm. to 2.25 mm. 
Wadithy Se" Wh 52! Be eee Z STO Ke 
Depth: 4/0852 AGRE 4 

b. Sensory Cushion. The sensory ridge, or cushion, in the base of 
the otocyst is not prominent, as that part of the sac floor upon which 
the sensory hairs are borne is but slightly elevated above the rest (Fig. 
38, set. ot.), and, contrary to the conditions found in the two forms already 
described, the sensory surface is nearly horizontal, instead of being 
vertical or oblique. The arrangement of the hairs is shown in Figure 
40 (Plate 8). Three sets can be distinguished, corresponding to the 
divisions of the otic nerve, —a median, a lateral, and a transverse or 
posterior. The first and third are nearly straight, the second sickle- 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 201 


shaped. The “median” set consists of a single nearly straight row, 
running from the posterior angle of the sac obliquely forward and 
mediad, back of which there are two or three shorter, irregular rows 
of scattered hairs. The lateral set consists of two concentric rows, 
which have the form of a crescent or the blade of a sickle, the handle of 
which is represented roughly by the nerve trunk connecting the bristles 
with the brain. The hairs of the outer row are much larger than those 
of the inner series. At the tip of the sickle blade the area covered by 
the bristles expands, and the hairs are arranged in 4 or 5 irregular 
rows. Behind the proximal end of this sickle-shaped double row of 
bristles is a short row of very large hairs, the posterior set (Fig. 40, 
set. p.), usually nine in number, which extends transversely across the 
posterior portion of the sac immediately in front of its pointed base. 
Matrix cells are found in the region directly beneath the hairs, as in the 
other forms described (Plate 8, Fig. 37), and the nerve cells with their 
peripheral fibres lie below the chitin, either just within (lateral set), 
or slightly posterior to (median and transverse sets) the rows of hairs 
(Plate 8, Fig. 40). By looking down upon the floor of the sac one can 
make out numerous small pores (represented in Figure 40 by minute 
circles), which penetrate the chitinous wall in that portion of the floor 
which is inclosed by the sensory bristles, especially in its lateral part. 
In transverse sections some of these pores are cut through, and it then 
appears that they connect with the ducts of multicellular glands which 
are located in the tissues beneath. One of these glands with its duct 
and pore is shown in Figure 39. It is apparently similar to the tegu- 
mental glands found in different parts of the lobster and figured by Her- 
rick (95, Cut 5, p. 77). In Cambarus these glands evidently supply the 
secretion which attaches the otoliths to the pinnules of the otocyst hairs. 

ce. Structure of Hairs. This has been described in some detail by 
Hensen (’63), to whose descriptions I have not much to add. The 
hairs are very similar in structure to those of the lobster. Their 
number varies greatly in different individuals, but is usually over 200. 
The straight, or only slightly curved, shaft is heavily fringed, and borne 
on the customary spherical base. Their dimensions are : 

Length, from 65 » to 175 p. 
Diameter, “ 15 4“ 18 p. 

A transverse section of the shaft near its base has the peculiar shape 
shown in Figure 35 (Plate 7). This modification of the form of its 
wall, found also in the otocyst hairs of the lobster, doubtless renders 
the shaft more rigid than if it were a simple hollow cylinder. 


202 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


The shaft, as already noted, is nearly straight, but it is attached to 
the floor of the sac in such a way as to make a very small angle with 
its surface, being, in fact, nearly parallel to it. Thus in Cambarus the 
bending has taken place at the base, not, as in Palemonetes and 
Crangon, in the shaft itself, In these two forms the tendency of the 
shaft to bend must be aided, if not caused, by the weight of the otoliths 
attached to the slender tips of the hairs. In the lobster and crayfish 
the modified form of the shaft makes it too rigid to thus give way, and 
the bending, if any, must take place at the thin, membranous basal 
sphere. 

d. Formation of Hairs. (Not studied in Cambarus.) 

e. Otoliths. These are composed of large grains of sand distributed 
mostly within the circle of hairs, and supported in part by them. As 
the sac has a large opening, they are readily taken in through it after 
each ecdysis. 


2. Innervation of the Otocyst. 


As the crayfish was well adapted for work with methylen blue, a 
large number of preparations of the sensory nerve elements were made, 
not only of the hairs of the otocyst, but also of the other sensory 
bristles. The nerve supplying the otocyst issues from the ventral 
surface, instead of the anterior end, of the brain, and at once passes 
forward with a slight lateral curvature to the pointed posterior end of 
the sac, beneath which its fibres spread out to the different hairs. It 
divides roughly into two strands, one of which passes obliquely forward 
and mediad to supply the median set of bristles (Plate 8, Fig. 40), 
while the other follows the course of the lateral sickle-shaped set, lying 
on the concave side of the two rows, to which it gives off fibres along 
its whole course. Before this division of the nerve takes place, a few 
large fibres run out from it on the lateral side (Fig. 40) to supply the 
short transverse row of large bristles (Plate 7, Fig. 33). 

The sensory nerve cells lie immediately beneath the hypodermis, and 
their peripheral fibres run in a plane parallel with the floor of the sae. 
In the case of the transverse rowof large hairs, the nerve cells are 
situated about 450 w posterior to the bases of the shafts, their peripheral 
fibres being therefore nearly half a millimetre in length. This is 
accounted for by the position of the new hair tube during the period of 
its formation between moults, when it extends back from the base of 
the functional shaft 350 1; the distance from base of hair to ganglion 
cell must consequently be somewhat greater than this. 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 203 


a. Number of Nerve Elements to a Single Bristle. The number of 
cells and fibres for the whole ‘sac could not be determined with exact- 
ness, as other sensory elements, supplying tactile hairs, are mingled with 
those of the otocyst. But in the short transverse row of large hairs, 
the cells and fibres are sufficiently isolated to allow of their being 
counted in serial sections. There are but nine hairs in that row, and if 
the nerve elements supplying them were twice as numerous, it would be 
at once apparent. The cells always occur singly, and their fibres run 
separately and parallel with one another to the bases of their respective 
hairs (Plate 7, Fig. 33). The number of each was counted many 
times, and it is certain that the number of ganglion cells and peripheral 
Jibres exactly equals the number of hairs. Whole preparations of these 
nerve elements stained with methylen blue gave regularly nine ganglion 
cells and fibres supplying the nine sensory hairs. In these few otocyst 
hairs, at least, there is, then, but a single nerve element supplying each. 

In the tactile hairs of the scaphognathite of the second maxilla, many 
methylen-blue impreguations gave conditions like that shown in Figure 
34 (Plate 7), only one sensory nerve element being stained. In the 
short spike-shaped bristles found on this same appendage, from three 
to five ganglion cells (Plate 7, Fig. 32, cl. gn.) were usually found sup- 
plying each bristle. 

In the olfactory bristles of the antennule, the conditions were the same 
as those already described and figured for Palemonetes, though fewer 
elements compose each spindle-shaped group of cells. 

b. Peripheral Terminations. No. branching of peripheral nerve 
fibres was observed in any sensory elements, though many were 
traced the whole length of an appendage. In Cambarus the fibres 
end always at the base in the otocyst hairs (Plate 7, Fig. 33). There 
is often a marked increase in the diameter of the fibre near its termina- 
tion, caused either by the staining of its sheath at this point, or by a 
partial separation of the component fibrille. Tactile hairs show similar 
conditions in their nerve endings (Plate 7, Fig. 34). 

The fibre strands of the olfactory bristles were, on the contrary, traced 
into the shaft some distance, where they apparently end free. Thus in 
the crayfish, we have a distinct difference in the innervation of the two 
types of sensory hairs, which serves to confirm the statements made 
ecncerning the conditions in Paleemonetes and Crangon. 

e. Central Terminations. The otocyst nerve in Cambarus is large 
enough to be dissected out and traced to the ventral side of the brain, 
which it enters lateral to the larger antennular nerve. Its point of en- 


204 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


trance isa little to one side of the median plane of the brain, opposite the 
posterior end of the globulus (Plate 9, Fig. 41). Its fibres run backward 
and dorsad, just lateral to those of the antennular nerve, and end in a 
neuropil directly anterior and median to that of the second antenna 
(Fig. 41, n. ot.) The individual fibres end by branching into fine 
fibrillations, which could be traced only a short distance through the 
diffusely stained mass of fibrillar tissue about them. 

d. Histology of the Nerve Elements. The sensory nerve fibres of 
Cambarus are relatively smaller than those of Palemonetes. Imme- 
diately after leaving the ganglion cell each measures about 3yu in 
diameter, but becomes smaller as it runs distally, until near the point 
of ending, where it again enlarges to its original size. In well differen- 
tiated methylen-blue stains, fibrillar structure is clearly brought out. 
Longitudinal sections, and whole preparations of continuous fibres, show 
fibrillations similar to those figured for Palaemonetes. 

The sensory nerve cells are relatively large ; they measure from 15 to 
18u in diameter, and being bipolar are spindle-like in form. Their 
nuclei are spherical and from 10 yu to 12m in diameter. The cytoplasm 
of the cell never shows any evidence of fibrillations, but in methylen-blue 
impregnations there is a faintly staining zone directly about the nucleus ; 
the remainder of the cytoplasm takes on a deep blue color. This dif- 
ference in staining qualities may be due to the unequal distribution of 
chromatic substance in the cytoplasm. 

The myelin sheath, so characteristic for the nerve fibres of Paleemo- 
netes and Crangon, is not found in the nerve elements of the crayfish. 

3. The development of the otoryst was not studied in Cambarus. <Ac- 
cording to Reichenbach (’86) it is completely formed before the young 
animal leaves the egg. 


IV. Carcinus m=nas Leacu. (Green crab.) 


We now come to the second type of otocyst, which is found in all 
brachyuran Crustacea ; it is closed, and without otoliths. Mistaken by 
Bate (’58) for an olfactory organ, and figured by him in the larval 
stages of the crab, it has been described carefully in Carcinas meenas 
by Hensen (’63) alone. His account, although fairly accurate, is in- 
fluenced by his seeing a fancied resemblance between the otocyst and the 
vertebrate ear ; the figures he gives of different parts of the sac dissected 
out leave one somewhat in the dark as to the relative positions of the 
structures described. 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 205 


1. Structure of the Otocyst. 


a. Sac. The basal segment of the antennule in Carcinus is relatively 
large, and elongated laterally to such an extent that its width is nearly 
twice its length (Plate 9, Fig. 46). Along its dorsal wall there ex- 
tends transversely a distinct line dividing the chitin of the anterior part 
of the segment (lad. a.) from that of the posterior. This line of division, 
which reaches from the lateral margin of the segment three-fourths of 
the way across its dorsal wall, is rendered more prominent from the fact 
that the chitin posterior to it (/ab. p.) is much lighter in color thau 
that in front. 

If the antennule of a crab is examined directly after ecdysis, when the 
chitin is still very thin, soft, and uncalcified, this lighter colored area 
(Fig. 46, lab. p.) is found to be a fold, projecting forward over the ante- 
rior part ; and if its edge is lifted with a needle or fine pair of forceps, 
a transverse aperture is disclosed leading down to the lumen of the sac. 
This aperture extends from line 45 (Fig. 46) laterally down through 
the side wall of the antennule. There is, then, in fact, a free passage 
into the otocyst directly after moulting, a condition necessitated by 
the casting off of the old sac. But almost immediately after ecdysis, 
the opening is closed and its edges fuse together, probably owing to the 
simultaneous secretion of chitin by the hypodermis of the two surfaces 
which bound the orifice and are in direct contact. Figure 44 (Plate 9) 
shows at lab. p. the two surfaces which fuse. 

The form of the sac is very irregular, so much so that Hensen de- 
spaired of describing it. Its walls, like those of the forms already studied, 
are continuous dorsally with the calcified chitin of the antennule (Figs. 
42-48, Plate 9). The sac is thus suspended from the dorsal wall of the 
appendage. Although composed largely of thin chitin, one portion of its 
wall is much thickened and calcified (mal., Figs. 43-48, Plate 9). On 
account of its irregular outline measurements can be of only small value. 
The average of a number of measurements taken of the otocyst in speci- 
mens approximating 30 mm. in length, gave the following results : — 

Greatest length, 1.11 mm. 
coe iwidth, 1296 
« depth, 1.05 “ 

The seemingly contorted shape of the sac is caused by three protuber- 
ances or invaginations of its walls, which project into the lumen (Fig. A, 
and Plate 10, Fig. 55). Two only of these prominences are sensory and 
bear bristles (Fig. A, set. ta. and set. fil.). The third and largest of 


206 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 


the three (mal.), which projects from the lateral and posterior wall of the 
cyst, is without sensory organs of any kind. Its wall is irregularly 
curved and pitted (Plate 9, Fig. 47 mal.,), while portions of it are even 
calcified. At one point its walls are constricted to form a neck, which 

ears a large hammer-like head (Fig. 47). This is the “ Hammer” of 
Hensen, compared by him to the malleus of the vertebrate middle ear. 
Figures 43, 48, and A show the relative position of this hammer to the 


set. fil. 


set. l@. 


FIGureE A. 


Model of the lumen of the left otocyst of Carcinus, dorsal view, the upper wall of the sac 
removed. The cavity of the sac was modelled in wax from serial sections under a 
magnification of 50 diameters, and a plaster cast of the model photographed natural size. 
In making the cut this was reduced to a magnification of 33 diameters. a., anterior; 
m., median; set.’, group hairs; set. il., thread hairs; set. ta., hook hairs. 


rest of the sac. It serves merely for the attachment of the short, thick, 
powerful muscles of the antennule which keep the latter in almost con- 
stant motion, and has probably nothing whatever to do with the sensory 
functions of the otocyst. 

b. Sensory Cushions. Of the three projections noted, the remaining 
two are sensory and bear sensory hairs (Plate 10, Fig. 55, set. ta., 
set. fil.). The smaller of these (set. ta.), located on the median portion 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 207 


of the posterior wall of the sac, bears a number of hairs with hooked 
shafts. The surface bearing these lies in a nearly vertical plane. From 
its position and the shape of its hairs this prominence is comparable 
to the sensory cushions upon the surfaces of which the otoliths are 
lodged in Paleemonetes, Crangon, and the crayfish. Irregularly disposed 
matrix cells are situated in clusters immediately beneath the hooked 
hairs (Plate 10, Fig. 50), and deeper in the tissues are the ganglion 
cells of the nerve fibres which supply the bristles (Fig. 50, e/. gn.). In 
the larval stages of the crab this sensory cushion is relatively much 
larger. It extends through half the length of the sac, and its hairs 
are in contact with the otoliths which the sac then contains. Pores of 
tegumental glands penetrate the chitin of this prominence, as they do 
that of the sensory cushions in the crayfish and lobster, although found 
in no other part of the sac. These glands secrete a substance which, in 
the larval crab, attaches the otoliths to the tips of the hairs. Their 
presence in the adult crab is evidence in favor of tht homology of this 
cushion with that described for otocysts containing otoliths. 

The other sensory cushion is much larger, and is produced by a 
partial invagination of a portion of the median and anterior walls of 
the sac, which forms an oval prominence (Fig. A; Plate 9, Fig. 48; 
Plate 10, Fig. 55, set. fil.). It is nearly 0.5 mm. in diameter, and its 
surface, making an angle of about 45 degrees with both the transverse 
and sagittal planes of the animal, inclines backward, inward and down- 
ward (Plate 9, Fig. 45). Its ventral portion is shown in transverse 
section in Figs. 47 48. The chitin of this cushion is very thin ; upon 
it is arow of long delicate hairs, called by Hensen (’63) “ Fadenhaare,” 
or thread-hairs. This row runs down somewhat obliquely from the 
upper side of the prominence to its ventral margin near the floor of the 
sac, its dorsal end being the more anterior of the two (Fig. A, set. jil.). 

This sensory cushion is also found in the sac of the larva, and 
the bristles it then bears are similar to those found projecting free into 
the lumen of the lobster otocyst from its median wall (Plate 5, Fig. 
26, sel. m.). The prominence we are now describing in Carcinus is 
probably therefore simply a further differentiation of the slight projec- 
tion noted in the sac of the lobster. 

Matrix cells send delicate processes into the hairs, as in those of pre- 
ceding species; the ganglion cells are situated directly beneath the 
hypodermis, but some distance posterior to the bases of the hairs (Plate 
10, Fig. 53, cl. gn.). 

No gland pores are present, nor are they needed, as the thread 


208 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 


hairs are never in contact with the otoliths, even in the larval 
stages. 

A third region, on which sensory hairs are located, is found at the 
extreme lateral side of the sac, beneath the fused lips of its opening 
(Fig. 4; Plate 9, Fig. 42, set.’). There is only a slight prominence, the 
surface bearing the hairs being nearly flat. The hairs are arranged in 
irregular fashion, somewhat like the groups of otocyst bristles situated 
near the aperture of the sac in the crayfish and lobster. Numerous 
groups of matrix cells lie directly below these hairs, but no nervous 
structures could be distinguished in their vicinity. 

The great hammer-like prominence, which serves for the attachment 
of the antennular muscles, separates the sac roughly into an upper, 
anterior chamber and a lower, posterior one. The first of these com- 
partments is again partially separated into two by the anterior sensory 
prominence, which nearly meets the “hammer.” These three chambers, 
into each of which sensory hairs project, were likened by Hensen to the 
semi-circular canals of the vertebrate ear, and the sensory regions to the 
criste acustice. As the compartments are in free communication, are 
not at all canal-like in form, and are arranged in no definite positions 
relative to each other which might be of functional importance, there 
seems to be no more logical reason for making such a comparison than 
for comparing the hammer-like projection of the otocyst to the malleus. 
The apparent division of the otocyst into three compartments is not a 
modification for the purpose of increasing its usefulness as a sense organ, 
but evidently a condition brought about mechanically by the differen- 
tiation of the “hammer” along lines which would make it better 
adapted for the attachment of muscles. 

c. Structure of Hairs. The hairs, as already indicated in describing 
the sensory regions, are of three kinds. Hensen’s account of them is 
fairly good. He divides them into the following classes: (1) hook 
hairs (Hakenhaare), (2) thread hairs (Fadenhaare), and (3) grouped 
hairs (Gruppenhaare). 

(1) The hook hairs are found on the posterior vertical cushion (Fig. 
A and Plate 10, Figs. 50, 55, set. ta.) arranged in a very irregular 
curved row. They vary from 25 to 31 in number, and are relatively 
very small, averaging 49 u in length and 4 4 in diameter. Their shafts 
are hooked, often bent nearly double, and are sparsely fringed near the 
tip, if at all. The base is enlarged, as is usual in otocyst hairs, but 
not so markedly as in the forms already studied. Instead of being 
attached to a large spherical membrane, the base of the shaft is set 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 209 


into a cup-shaped depression and so labilely fastened to the chitin of 
the sac wall (Plate 10, Fig. 51) that the hair can sway freely in any 
direction, as if it were attached by a ball-and-socket joint. This cup- 
like depression is characteristic of all the otocyst hairs of Brachyura. 

The hook hairs are present in the otocyst of the Megalops larva of 
Carcinus, and are there relatively much larger ; they extend over a large 
portion of the posterior end and floor of the sac, the curved row of 25 to 
30 hairs occupying two-thirds of its length. As the otocyst is open at 
this stage, it contains numerous otoliths, and these are either im contact 
with, or attached to, the tips of these hairs. Measurements of a number of 
these larval hairs were made in the Megalops and the stage succeeding 
it, and a comparison of these with the same hairs of adults is made in 
the following table : 


: Average Length Average Diameter 
ma ot of ten Hook of ten Hook 
YBbe Hairs. Hairs, 


Adult (80 cm. long) 1.96 mm. 49 u 


Young crab 0.24 mm. AT u 


Megalops larva 0.21 mm. 46 u 


This table brings out the interesting fact that the hook hairs of a 
Megalops larva, of a young crab and of an adult are of nearly equal 
size, although the otocyst of the adult is nearly ten times as long as 
that of the Megalops, and over eight times that of the young crab. On 
measuring the thread hairs to see if the conditions there were the same, 
it was found that in the adult they were three and a half times as long 
as in the Megalops stage; the thread hairs thus more than tripled their 
length, while the hook hairs remained constant. The number of hook 
hairs is approximately the same in the Megalops otocyst and in the sac of 
the adult. Their arrested development may be explained by the fact 
that they are true otolith hairs; when the otocyst becomes permanently 
closed, otoliths can no longer enter the sac, and these hairs, as they lose 
their original function, do not grow part passu with the other hairs of 
the otocyst, but remain unchanged. They do not degenerate and 
become entirely functionless, for they are still innervated in the adult 
crab, and, though sac after sac is shed and new ones formed without an 
otolith’s finding its way into the organ, they still retain the peculiar 
form of the original otolith bristles. 


210 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


We are thus led to regard the hook hairs of the crab as homologues 
of the otolith hairs of Macrura, and for these five reasons :— (1) The 
similarity in their structure. (2) Their similarity in position at the 
posterior end of the sac. (3) Otoliths are in contact with the hook 
hairs in larval stages, though not in the adult. (4) When the otoliths 
disappear, the development of the hook hairs is arrested. (5) Gland 
pores open through the chitin of their cushion, as they do through that 
of the crayfish and lobster, although they are not found in the other 
sensory regions of the sac. 

(2) The thread hairs are the largest, the most highly differentiated, 
and probably the most active sensory bristles of the otocyst. There 
are about thirty of them, arranged upon the large anterior sensory 
cushion in a regular row (Fig. A, set. fil.). These hairs are extremely 
attenuate. Measuring only two or three uw at the base, the straight or 
slightly bending shaft averages 320 in length; it is unfringed save 
at the very tip, where for a short distance it bears two rows of ex- 
tremely delicate pinnules. A peculiarity of this fringed tip is that 
it is not a coutinuation of the main shaft of the hair, but seemingly 
a diminutive hair in itself, sprouting from the latter. It makes a 
slight angle with the main shaft, the end of which projects a short 
distance beyond the base of the offshoot (Plate 10, Figs. 53, 54). 
The shafts of these hairs are directed out laterally, and slightly pos- 
teriorly, into the fluid contents of the sac, and they are so delicately 
attached at their bases that the slightest jar imparted to the liquid 
in which they float is sufficient to set them swaying. In alcoholic 
material they break off very easily. The shaft decreases somewhat in 
diameter towards its base and then suddenly enlarges. This enlarge- 
ment is attached to the floor of a deep cup-like socket, the orifice of 
which is large enough to give ample play to the shaft in its movements 
(Fig. 53). 

Straight attenuate hairs are found in the otocyst of the Megalops 
larva having the same relative position in the sac as the thread hairs 
of the adult. These hairs are aot in contact with otoliths, but each 
shaft is fringed with filaments throughout its whole length. They 
become differentiated in later stages into the peculiarly modified thread 
hairs. Hairs similar to those of the Megalops larva just described 
are also found in the otocyst of the adult lobster, situated on the 
median wall of the sac and projecting free into its lumen. They are 
similar in both larva and adult, and are probably in function accessory 
to the otolith hairs. They may be homologues of the thread hairs, 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. PAIL 


which, in the crab, with the disappearance of the otoliths, have taken 
on the chief functional activity of the otocyst, formerly vested in the 
hook hairs. 

(3) The group hairs (set.’) form the third and most numerous class of 
the otocyst bristles of Carcinus. Irregularly distributed in the most 
lateral corner of the sac (Fig. A,) on a flattened portion of the wall 
ventral to the closed margins of the aperture (Plate 9, Figs. 42, 47; 
Plate 10, Fig. 55), they are unlike any of the otocyst hairs found in 
Macrura, being short, thick, and blunt, without a trace of fringing fila- 
ments (Plate 10, Fig. 49). They are 1104 to 135 long and 124 to 
14 in diameter. There are nearly 200 of these hairs, forming one 
large irregular group. They do not occur in the Megalops otocyst, 
therefore they must be developed at some later period. They may 
possibly be degenerated tactile hairs which in the formation of the 
otocyst have been folded into its cavity. Their proximity to the aper- 
ture of the otocyst makes this supposition highly probable. Their 
shafts are set into depressions in the sac wall, and, like the other oto- 
cyst hairs, they can sway freely on their bases. 

d. Formation of Hairs. The hairs are formed in Carcinus, and in 
the Brachyura generally, after the method already described in 
Palemonetes. From the presence of a cup-like depression at the 
base of each shaft, instead of the large spherical membrane found in 
the Macrura, it might be inferred that the cup results from the in- 
complete evagination of the hair. 

e. Otoliths are entirely wanting in the adult otocyst, but are present 
in those larval stages where the sac is still open. They consist, as 
usual,.of grains of sand, which in this case are very small, for the sac 
itself in these stages is less than 0.3 mm. in length. They can readily 
be introduced into the otocyst of the Megalops, as its aperture is rela- 
tively large. When in a succeeding stage the sac is cast off with its 
otoliths at ecdysis, the aperture of the new cyst closes at once, and 
no foreign particles can enter it ; henceforth it is without otoliths. 


2. Innervation of the Otocyst. 


The general course of the otocyst nerve is shown in Plate 10, Figure 
55 (n. ot.). As in the forms previously described, the sac lies in close 
proximity to the brain, and its nerve is consequently short. It is 
given off with the antennular nerve from the anterior end of the cen- 
tral organ, and its course for a short distance is directly lateral, until 
the base of the antennule is reached. At this point the antennular 


PAM BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 


nerve (n. at.1) turns straight forward, while that of the otocyst divides 
into three branches (Fig. 55, n. ot., n. ot.!, n. ot.!). The most median 
and largest of these runs forward to supply the thread hairs; the 
middle branch goes directly to the posterior sensory cushion, which 
bears the hook hairs; while the third and lateral offshoot takes a 
nearly straight course along the posterior wall of the sac and supplies 
the tactile hairs of the antennule, and possibly the group hairs of the 
otocyst. The ganglion cells of the hook hairs are some distance pos- 
terior to the hairs and arranged in an irregular scattering group 
(Plate 10, Fig. 50, el. gn.). Those of the thread hairs are lateral and 
posterior with reference to their hairs, lying immediately beneath the 
hypodermal cells of the sensory cushion, and forming an irregular single 
row, which is nearly parallel to the row of thread hairs (Plate 10, 
Fig. 53, el. gn.). 

a. Number of Nerve Elements to a Single Bristle. The nerve ele- 
ments of the thread hairs were brought out clearly and completely by 
methylen blue and by Vom Rath’s platinic-chloride method. The 
conditions found in a number of preparations are shown in Figure 53, 
where there is but a single element for each hair. This particular 
preparation was obtained with methylen blue, but the results were 
verified by Vom Rath’s method. Counted in serial sections, the num- 
ber of hairs and ganglion cells were approximately equal. 

By the same method of counting, the elements of the hook hairs 
gave like results. In one case there were thirty hairs and thirty- 
one cells. No ganglion cells could be made out near the group hairs, 
nor any fibres supplying them. Certain clusters of cells are found 
directly beneath their bases, but their large peripheral processes, irregu- 
lar outlines, and lack of central fibres marked these as matrix rather 
than nerve cells. 

Here in Carcinus, then, as in the macruran forms described, there 7s 
but one nerve element to each otocyst hair. 

The distal segment of the antennule was by chance sectioned in 
making preparations of the otocyst, and when stained with iron hema- 
toxylin, the innervation of the olfactory hairs found in that region was 
sharply brought out (Plate 10, Fig. 52). As in the examples of this 
type of hair already described, « large spindle-shaped group of about 100 
ganglion cells sends a strand of nerve fibres to the base of each shaft. 
These cells are relatively small and situated 0.5 mm. posterior to the 
hairs they supply. In Figure 52 a single nerve element is shown 
diagrammatically in black. 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 213 


b. Peripheral Terminations. As seen in Figure 53 (Plate 10), the 
terminal fibres going to the thread hairs enter the pore at the base of the 
cup-shaped depression, pass up into the enlargement of the hair shaft, 
and there end free. In fact, there is in these hairs no functional neces- 
sity for the further continuance of the fibre into the shaft. Since the 
hairs project free into the liquid of the sac, if the otocyst is jarred or 
tilted, the shaft does not itself bend, but sways backward and forward 
upon its base. It is therefore at the base that the stimulus must mani- 
fest itself, and it was there in every case that the fibres were found to 
end, 

In the olfactory hairs, on the other hand, the nerve fibres continue up 
into the large hollow shafts for some distance (Plate 10, Fig. 52, set. olf). 
The olfactory hairs of Carcinus thus differ in their innervation from those 
of the otocyst, both in the number of nerve elements supplying each hair, 
and in the peripheral nerve endings. In the bristles of the otocyst there 
is but a single nerve element, and it ends free at the base of the hair 
without branching. In the olfactory hairs there may be a hundred ele- 
ments or more which end in the shaft of a single hair. 

e. Central Terminations. Entering the brain in front of, and just 
median to, the globulus, and ventral to the optic centres, the fibres of 
the otocyst nerve run straight back and enter the fibrillar mass (Plate 
10, Fig. 55, n’pil. at.1), called “the neuropil of the first antenna” by 
Bethe (’97), who has described the central endings of the antennular 
nerve of Carcinus. ‘The fibres of the antenuular nerve end in a connected 
neuropil just median to those of the otocyst. Bethe judged from his 
physiological experiments that there should be certain fibres from the 
otocyst ending in the globulus. He was not able to demonstrate such 
endings with methylen blue, nor was there any evidence of their exist- 
ence in my preparations. According to Bethe the fibres from the oto- 
cyst end by the separation of their fibrille in the neuropil. Lack of fresh 
Carcinas material prevented the verification of his work, but I have 
described similar conditions in the shrimp and crayfish. 

d. Histology of the Nerve Elements. As the finer structure of the 
elements of the central nervous system has been fully described by Bethe 
(98), it is unnecessary for me to say anything on that matter, and 
only a few words need be added here as to the histology of the peripheral 
nerves and cells. The peripheral nerve fibres are much smaller than 
in Paleemonetes or Crangon, and are without.a myelin sheath. The 
peripheral ganglion cells are relatively large, averaging 12 u in diameter. 
They are of the typical bipolar form, and are much elongated (Plate 

VOL. XXXVI. — NO. 7 4 


214 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


10, Fig. 50, cl. gn.). Their nuclei are nearly spherical, and contain at 
least one large deeply staining nucleolus. No special preparations were 
made for the purpose of demonstrating fibrillz in either nerve cells or 
fibres. Bethe found them in all fibres, and traces of them in the cells of 
the brain. 


3. Development of the Otocyst. 


For the purpose of comparison with development in the lobster, the 
antennules of the first five free swimming larval stages of Carcinus were 
dissected out, stained and examined in toto. By this means it was 
ascertained that there is no functional otocyst in the Zoea stages. 

(a) The first Zoea shows no trace of invagination in its antennule. 
There is, however, an aggregation of nuclei beneath the chitin of the 
region where the otocyst is to appear. 

(6) The second Zoea shows a slight depression on the dorsal side of 
the antennule, and its basal portion has begun to widen. 

(c) In the third Zoea this widening has increased, and the lateral wall 
of the antennule has now formed a rounded protuberance. The invagi- 
nation has increased in size and depth, but no hairs nor otoliths are yet 
contained in it. 

(d) At the Megalops stage we find that a sudden development has 
taken place, as in the fourth larval stage of the lobster. The Zoea has 
by a single moult become metamorphosed into a Megalops, and the oto- 
cyst changed from a shallow depression to a nearly closed sac, contain- 
ing sensory hairs and otoliths. Two sensory cushions are present: one 
of these, posterior and median, bears 25 to 30 hooked hairs, upon the 
tips of which otoliths rest ; the other prominence projects from the 
anterior portion of the median wall, and bears a vertical row of about 30 
hairs, the shafts of which are directed laterally. These hairs are long, 
attenuate, and well fringed with delicate filaments. They do not come 
into contact with the otoliths, and, as already noted, they develop into 
the thread hairs of the adult ; those of the first sensory cushion described 
correspond to the hook hairs of the mature crab. The third type of hair 
found in the adult is not developed at this stage. The aperture is 
anterior and lateral in position, and extends transversely across the 
antennule. 

(e) The next stage examined was that of a young crab probably of 
the stage immediately succeeding the Megalops larva. The otocyst is 
slightly larger, and its opening is already nearly closed. As a result, only 
a few small otoliths were contained in it. 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 215 


The otocyst of Carcinus thus resembles very closely in its development 
that of the lobster. In both there is no trace of the organ in the newly 
hatched larvee, and for three successive moults it is not functional. In 
the fourth larval stage, with a sudden metamorphosis of the animal’s 
general form, the otocyst is also rapidly changed from a mere depression 
to an active, well-developed organ. The significance of these sudden 
correlated transitions will be seen when the otocyst is considered 
physiologically. 


C. THEORETICAL CONSIDERATIONS. 


1. Comparison of the Otocyst with the Vertebrate Har. 


The otocyst has been compared by many investigators to the auditory 
organ of vertebrates. Leaving their functions entirely out of account, 
how far do the two correspond in structure ? 

The otocyst of Macrura consists of an open sac, a sensory prominence, 
bristles, and otoliths resting upon them ; essentially the-same conditions 
as are found in the ear of Myxine, though the latter has five sensory 
regions instead of one. The otocyst of macruran decapods might thus 
be well compared to an isolated ampulla in the ear sac of Myxine, and 
the sensory cushion to a single crista acustica. 

In the Brachyura the organ is still more highly differentiated. The 
sac is closed, there are three sensory regions, and the hairs found on 
them project free into the lumen of the otocyst; otoliths are entirely 
wanting. The structure of the sensory apparatus is in this case similar 
to that of the cristz of higher vertebrates, and the sac itself resembles 
the utriculus. But there zs no portion of the decapod otocyst so differen- 
tiated as to bear more than a fancied resemblance to the semicircular 
canals, the middle ear, or the cochlea of higher vertebrates. 

Each crista acustica in vertebrates, however, is made up of separate 
elements, which may be compared to the sensory elements of the otocyst. 
Every auditory hair of the crista is developed from the exposed end of a 
specialized epithelial sense cell, which itself forms the basal part of the 
hair, and is supported in position by the other cells of the epithelium. 
It has been shown by both Retzius (’94) and Morrill (’98) that these 
epithelial sense cells of the criste in vertebrates are not true nervous 
elernents, as the auditory fibres are not continuous with them. Both 
the cell and its auditory hair taken together are to be compared to the 
bristles of the otocyst, in that they constitute a non-nervous end-organ. 


216 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


Their innervation is also essentially the same. In the vertebrate crista 
an auditory nerve fibre passing from the brain is connected with a bipolar 
nerve cell in the auditory ganglion, from whence its peripheral fibre ex- 
tends to one of the epithelial sense cells, ending with a slight enlarge- 
ment in close proximity to, or in contact with its base. The single fibre 
supplying each end-organ is never directly connected with the cell, nor does 
it ever run through it to the hair itself. The only difference between the 
peripheral endings just described, and those of the otocyst, is that in the 
hairs of the latter the fibres end free in the base of the hollow shaft, at 
the point where, from the structure of the hair, the greatest stimulus 
would be produced ; while in the vertebrate end-organ the nerve process 
is applied to the convex under-surface of the basal cell, which would 
transmit stimuli with an equal degree of intensity to fibres in contact 
with it at any point. 

The otoliths of the vertebrate ear are formed by secretion, while 
those of the crustacean otocyst are largely granules of sand taken into 
the sac from the exterior. In some Crustacea, however, such as the 
Myside, and in many other invertebrates, the otoliths are formed within 
the sac. 

In all decapods the innervation of the otocyst hairs distinctly differs 
from that of the olfactory bristles, not only as to peripheral termina- 
tions, but also in the number of nerve elements supplying each hair. 
As has been previously noted, the stimulus is transmitted by specialized 
cells or hairs to the nerve fibres of both the otocyst and the vertebrate 
ear, and is never applied directly to their endings. In either case only one 
nerve element is usually in contact with the terminal sense cell, and this 
is apparently ample to carry the isolated nervous message to the brain. 

With the olfactory sense it is different; in both vertebrates and 
Crustacea the chemical stimuli which produce the olfactory sensations 
act directly upon the nerve cells or their terminal fibres. In vertebrates 
portions of the nerve cells are exposed at the surface of the olfactory 
epithelium. In crustacea peripheral fibres from the ganglion cells of 
the olfactory nerve end free in the hollow, perforate bristles. In Nereis 
and the earth-worm, Langdon (95, ’00) has shown that the processes of 
the olfactory cells end free upon the surface of the cuticula, and com- 
pletely exposed to chemical stimuli; a similar condition has been shown 
by Lewis (98) to exist in two polychetous worms of the family 
Maldanide. 

The large numbers of nerve elements ending in each olfactory tube 
or bristle of decapod Crustacea may be accounted for by the fact that 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 217 


the stimulating chemical substances occur as slight traces only. In order 
that a sensation may be perceptible, apparently a large number of olfac- 
tory elements must be stimulated at once, for the larger their number, 
the stronger should be the sensation produced. ‘The olfactory bristles 
are located on the flagella of the antennules, a position most favorable for 
the reception of chemical stimuli, as the flagellum projects some distance 
in front of the animal and can be kept in constant motion. The number 
of the bristles is limited on account of the small surface to which they 
are necessarily confined, so that, if thousands of olfactory fibres are to 
function simultaneously, large numbers of them must be exposed to the 
chemical stimulus in the same hair. It is possible, too, that different 
nerve elements may be affected by different substances in solution; and 
that consequently many olfactory elements are necessary for each hair, 
in order that different chemical stimuli may be perceived. 


2. The Neuron Theory. 


The conditions found in the sensory nerve elements of the otocyst are 
favorable to the neuron theory, in so far as they confirm the generally 
accepted idea that the nerve fibres are each differentiated from a single 
nerve cell, and that fibre and cell taken together form a trophic unit. 
This conclusion is borne out not only by the structural conditions 
already described, where each fibre is connected with only one peripheral 
ganglion cell, but also by an experiment which I made by severing the 
otocyst nerve proximal to its ganglion ; in this case after the lapse of a 
few weeks degeneration of the sensory fibres took place back into the 
brain. 

As to the modifications of the neuron theory recently proposed by 
Apathy (’97) and Bethe (’98),—that the neurons are connected by 
fibrille, — the fibrillar structure of the fibres is confirmed by my prepara- 
tions, though no fibrillee could be demonstrated in the nerve cells. In 
regard to the definite connection of the neurons with each other by con- 
tinuous fibrils, such as Apathy figures and describes in the Hirudinee, 
my preparations gave no positive evidence; but the fact that the cen- 
tral fibrillations of the nerve elements of the otocyst could not be traced 
to determinate endings, makes it quite possible that such a direct com- 
munication between motor and sensory neurons may exist. While Bethe 
proved that there were more fibrillze ina motor fibre than extended into 
its central ganglion cell, and also, that some fibrillze entered the fibre by 
one branch and at once passed out by another, in no case did he trace 


218 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


a single fibril from one neuron into another. If such a connection 
between nerve elements had been demonstrated beyond a doubt, they 
might still be considered as distinct trophic units, and the interdigitating 
fibrils uniting them as the products of separate neuron cells. In the light 
of the important discoveries of Apathy and Bethe, however, the old 
view, that the nervous impulses are transmitted from sensory to motoi 
neurons by the simple contiguity of their dendritic processes, may have 
to be abandoned for the more reasonable assumption of direct fibrillar 
communication. 


PART II.— PHYSIOLOGY. 


As Bethe has well said, the best of anatomical knowledge concerning 
an organ cannot be taken as certain evidence of its functions. It is 
only after these functions have been experimentally demonstrated, that 
we may ascribe them with confidence to the organ in question. 

Have we, then, any experimental proofs that the decapod Crustacea 
hear? If so, is the otocyst the auditory organ ; if not, what is its func- 
tion? These are the three chief questions which I shall attempt to 
answer. 


A. HISTORICAL SURVEY. 


Up to the time of Delage (’87) the auditory function of the otocyst 
was accepted, and that alone. 

Minasi (1775) promulgated the idea that Crustacea could hear. The 
hermit crab, Pagurus, was more sensitive than man to sound vibrations, 
The tones of a distant bell, the striking of a clock, were, according to 
this worthy monk, perceived by Pagurus sooner than they were by 
him. 

Alianus (1784) notes that the fishermen of his time took Pagurus 
by means of music, 

All the older zodlogists have regarded the otocyst as an organ of 
audition. 

Hensen (63) was the first to get experimental data. From the 
anatomical conditions found in the otocyst of the lobster, he argues as 
follows: Here are 468 auditory hairs upon which otoliths rest. Of 
these hairs no two are of the same size ; they vary in a nearly continu- 
ous series from 0.72 mm. to 0.14 mm. in length; thus the volume of 
the largest is to that of the smallest as 140: 1. Comparing these 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 219 


ratios to those of the volume of organ pipes, we should have, ¢f the hairs 
responded to different sound vibrations, an auditory organ with a range 
of three octaves. 

To prove that his hypothesis was correct, sound waves were conducted, 
by a mechanical contrivance modelled after the middle ear of mammals, 
into the water of a vessel containing Mysis, the so-called auditory hairs 
of which were under observation by the microscope. When notes of 
a certain group were sounded on a musical instrument, a certain hair 
would vibrate and disappear from view. Others would also respond, but 
each to different sets of notes. 

Having proved that the different hairs responded to different sound 
waves, Hensen next determined that Crustacea would react to vibratory 
stimuli. A resonant bar of wood was floated in a vessel containing free- 
swimming individuals of the genera Mysis and Palemon. When the bar 
was struck, both forms responded by a strong leap away from the source 
of the sound. Palemon reacted even more strongly when rendered 
sensitive by gradual strychnine poisoning. 

Milne-Edwards (76), Jourdain (’80), Delage (’87), and many others 
have accepted the sense of audition in Crustacea as a fact. 

Garbini (’80, p. 192) uneritically remarks: “ Che i crostacei odano 
e indubitato; lo sanno anche i pescatori, i quali devono avvicinarsi loro 
in silenzio” (That crustacea hear is undoubted ; this the fishermen know 
well, who, when they capture them, approach in silence). 

Individuals of Palemonetes varians, which he kept in an aquarium, 
sprang backward at the slightest sound. 

Delage (’87) was the first to discover another function than that of 
audition for the otocyst. By cutting off or destroying the sacs, he 
proved that they functioned also as organs of orientation. Animals so 
operated upon (Mysis, Palemon, and Polybius among Crustacea) were 
unable to keep their normal upright position in swimming. Blinding 
intensified the effect, showing that sight aided in orientation. 

The otocyst may therefore, in his opinion, be compared to the sim- 
plest form of the vertebrate ear, — that found in Myxime, — where the 
semicircular canals and utriculus serve the purpose of orientation, the 
sacculus that of audition (to intensity of sound). In the otocyst of 
Crustacea both functions are performed, he believes, by the same 
organ. 

Verworn (’92) proved that the otocyst of Ctenophores served simply 
for orientation, not being sensitive to sounds. 

Bunting (’93) confirms the conclusions of Delage as to the function 


220 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


of the otocyst in geotropic orientation. When the otocysts of young 
crayfish were destroyed, especially if their chele were also removed to 
render their position in the water less stable, there was the same loss of 
power of orientation that had been observed by Delage. 

Kreidl (93), in order to avoid the disturbance to the normal condition 
caused by the removal of the otocysts, made use of the following in- 
genious experiment: Palemonetes newly moulted, and thus without 
otoliths, were placed in filtered water to which iron filings were added. 
The otocysts were soon filled with the metallic particles, the chele being 
used to convey them to the opening of the ear in the dorsal wall of the 
antennule. When now a strong electromagnet was held at one side of, 
and slightly above the sacs containing the iron otoliths, the shrimp 
would lean a little to one side, its dorso-ventral axis, normally coincident 
with the direction of gravity, pointing away from the magnet. This new 
position of the dorso-ventral axis is proved by mechanics to be the 
resultant of the two pulls, that of gravity and that of the magnet, the 
animal accommodating itself to the direction of the resultant of the two 
forces. If the magnet were held to the right of the animal, the otocysts 
would be stimulated in precisely the same way as by gravity alone when 
the shrimp’s dorso-ventral axis is artificially turned toward the right ; 
the result is that it attempts to recover its normal position with reference 
to gravity, and thus turns its vertical axis away from the magnet. Kreidl, 
going a step further than his predecessors, affirms that the otocysts are 
not auditory, but exclusively static in function. Thus they should be 
called stato-cysts, not oto-cysts. 

Still further evidence as to their static function is supplied by Clark 
(96). The compensation movements of the eyestalks of the fiddler 
crab (Gelasimus pugilator) and the lady crab (Platyonichus ocellatus) 
were observed. ‘Tilting a normal animal about its antero-posterior axis 
gave a parallel compensating movement of the eyes through an angle 
of 35° to 45°, whether the tilting was to the right or left. On rotation 
about the dorso-ventra]l axis, no such movements are shown, though 
when rotated about the lateral axis, the animal’s eyes moved in the 
opposite direction through an angle of 35°. 

If both otocysts were removed, these compensative movements were 
much reduced, and the general movements of the crab also became 
very uncertain. 

After removal of one otocyst 94 per cent of the animals showed on 
rotation toward the uninjured side less compensation than uninjured 
animals. Blinding produced only a slight reduction in the compensatory 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. aa 


motions, but when, in addition to this, both otocysts were destroyed, 
compensatory movements completely disappeared. 

Bethe (97), in his physiological work on Carcinas mzenas, confirms 
Clark’s results. Ina previous paper he (’95*) observes that Mysis can 
hear after the otocysts have been destroyed, but with difficulty ; also that 
the animals are more sensitive to low tones than to high. 

Thus, until 1898 three views were held as to the function of the 
otocysts : 

(1) That they are purely auditory organs (Hensen and the earlier 
zoOlogists). 

(2) That they are both auditory and static in function (Delage and 
Bethe). 

(3) That they are purely static in function, i. e. organs of orientation 
(Kreidl, Clark, and others). 

‘To determine whether decapod Crustacea really hear, and if so, 
whether the otocyst is the organ of audition, is the aim of two papers 
by Beer (’98, ’99). 

In criticising the conclusions reached by Hensen and Bethe, Beer 
remarks in his first paper that, because decapods were made to react to 
different sounds, does not prove that these Crustacea responded to true 
sound, or that they heard. These reactions may have been due to their 
feeling vibrations transmitted to the water from the walls of the vessel 
in which they were confined, —a tactile reaction, or, to use Bethe’s term, 
a “tango-reflex.” Experiments with sounds produced in the air Beer 
considered superfluous, as it is a well-known physical fact that most of 
the sound waves are reflected from the surface of water. 

Beer found that Crustacea reacted strongly to sounds produced in the 
water by striking partially submerged bells, jars, etc., but only when 
they were not at a greater distance from the source of sound than that 
ut which vibrations could be detected by the hand immersed in water. 
The animals responded more strongly when near the walls of the vessel ; 
but vibrations could be felt by the hand also in this position more dis- 
tinctly, even though further removed from the source of the sound. 

For animals well supplied with tactile organs, he regards pure sound 
or pure audition as impossible; because vibrations could be felt as soon 
as heard, and, this being the case, audition would be useless. 

On removal of the otocysts, Palemon and Palemonetes still responded 
to sound waves produced in the water. There was, however, a slight in- 
hibition of the customary reactions, therefore the hairs of the otocyst 
are probably slightly tactile as well as static in function. 


222 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


From experiments.on many different species of Crustacea, Beer (’98, 
p- 31) concludes: ‘* Wir haben gute Griinde, dem in Rede stehenden 
Sinnesorgane der Krebse statische Functionen zuzuschreiben, und haben 
vorlaufig gar keinen Anhaltspunkt, ihm Horfunctionen, ja den Krebsen 
iiberhaupt Gehorsinn, zuzuschreiben.” 

Hensen’s statement that the free auditory hairs of Mysis vibrated to 
different musical notes is simply an interesting physical fact. Hairs on 
the back of one’s hand will do the same, but they are not auditory. 
The true sense of hearing is lacking not only in Crustacea, but probably 
in all other water-inhabiting animals lower than Amphibia, especially in 
invertebrates. 

Beer thus comes back to the opinion of Johannes Miiller (’37) ex- 
pressed sixty years before: That in most invertebrates we find nothing 
comparable to the ear; and any reaction to sound vibrations should be 
attributed to a tactile rather than to an auditory sense. 

A few months later Beer (’99) brought out a second paper, describing 
his experiments with blind shrimps, and answering a criticism of his pre- 
vious work by Hensen (99). Here the auditory sense, he urges, ought 
to be intensified, all possibility of sight entering as a factor into the 
experiments being effectually eliminated. The conclusions reached by 
him in his earlier work are verified in this. 


General Criticism. 


It is a noteworthy fact, that in the experimental work done to deter- 
mine the function or functions of the otocyst, few of the investigators 
have acquainted themselves with the finer structure of the organ under 
consideration ; one of the essentials for successful physiological work is a 
complete knowledge of the anatomical side of the subject. This is well 
illustrated in Bethe’s work on the brain of Carcinas, where anatomical 
facts, obtained by means of methylen blue, laid the groundwork for his 
later confirmatory experiments. 

Since the dissections by Hensen, little or no morphological work has 
been done on the otocysts of the Brachyura, yet a deal of physiological 
work has been attempted. 

The experiments of Beer are beautifully worked out, and logical in 
sequence ; yet, while he tried experiments on water-inhabiting animals, 
no attempt was made to experiment on amphibious decapod Crustacea, 
such as the fiddler crab. These animals, spending, as they do, a good 
share of their life on land, would certainly have more need of an auditory 
organ than decapods which are always beneath the surface of the water. 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 223 


B. EXPERIMENTS AND OBSERVATIONS. 
I. The Otocyst as an Auditory Organ. 


That the responses of water-inhabiting animals to atmospheric sounds 
is nothing more than a myth, has been too well proved by Beer to need 
further investigation. The well-known physical fact that the larger 
part of the sound waves are reflected from a liquid surface is enough in 
itself to confute fables of fishes and crustacea hearing, and coming to be 
fed at the sound of a bell. But since in the case of responses of decapod 
Crustacea to sound vibrations conducted into the water, the experiments 
of Beer contradict Hensen’s earlier results, repetition of Beer’s work, 
though perhaps not absolutely necessary, may not be out of place. 


Metuops. 


The shrimps to be experimented upon (Palzemonetes) were placed 
in glass vessels 40 cm. in diameter and 20 cm. deep. Sound waves 
were conducted to the water by means of a steel pipe one inch 
in diameter and about two feet long, which was firmly clamped at 
its upper end and projected into the vessel containing the shrimps; a 
brass rod was in some cases substituted for the pipe. The pipe and rod 
were set into vibration either by striking them with a hammer, or by 
drawing across them, bowlike, a strap of rosined leather. Sounds were 
also produced by striking glass jars suspended in the water, and by 
striking the sides of the aquarium itself. The movements made in pro- 
ducing the sounds were completely screened from the view of the 
shrimps by pieces of cardboard placed over and at one side of the 
vessel, a small aperture being left for observing their reactions. 

Palzmonetes could be made very sensitive to all nervous stimuli by 
leaving them over-night in sea water containing from 0.1 to 0.2% of 
sulphate of strychnia. This solution is fatal to a small fish (Fundulus) 
in five minutes; many of the shrimps die, but the sensory apparatus 
of those which remain alive is rendered abnormally acute. Blinding 
was accomplished by simply painting the eyestalks with a thick coat of 
lampblack and shellac ; the otocysts were removed by means of a fine 
hooked needle, with scarcely any other injury to the animal. 


1. Responses of Paleemonetes to Vibrations transmitted to Water. 


a. Normal Conditions. Under normal conditions, when sound vibra- 
tions were transmitted to the water, normal animals responded by a 


224 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


slight leap backwards or to one side, if the source of the sound was 
within a distance of 20 cm. Ifan animal happened to be near the side 
of the vessel, and the sound was produced near the opposite wall 40 em. 
distant, the response would be, not a darting away from the source of the 
sound, but a leap back from the side of the vessel toward the source of the 
sound. Again, if an animal was facing the side of the aquarium with 
its antenne in close proximity to it, and the opposite wall was sharply 
tapped with the finger-nail, or lightly with a hammer, the shrimp, as 
before, sprang away from the side of the vessel toward the source of 
the stimulus. The response was usually well marked, a leap of from 10 
to 15 cm. being made. 

b. Poisoned with Strychnine. The responses obtained were invariably 
much stronger and more uniform with animals poisoned by strych- 
nine in the manner stated above, than with normal shrimps. In other 
respects they were the same, and served merely to emphasize the results 
obtained by the first experiments. Blinded individuals showed _practi- 
cally the same reactions, but to make sure that the factor of vision 
was effectually cut out, the eyestalks of the shrimps in the succeed- 
ing experiments were all painted. 

c. Both Otocysts removed. Of animals from which both otocysts 
had been removed, all but one gave a more or less strong response 
to the sounds conducted into the water in which they were swimming. 
The reactions were not as marked, nor could they be produced at as 
great a distance from the source of the sound, as in the case of normal 
animals. Nine individuals were affected by the stimulus when at a 
distance of about 10 cm.; the rest, only when in still closer proximity. 
A slight jar imparted to the walls of the aquarium produced essentially 
the same responses as the transmission of sound to the water by means 
of the vibrating pipe or rod. Removal of the otocysts has, therefore, 
only a very slight inhibitory effect, upon the responses called forth by 
sound-wave stimuli in normal or strychnine-sensitized animals. 

d. Removal of Antenne and both Antennules. The removal of the 
antennze and antennules, which bear large numbers of delicate tactile 
hairs, very much reduced the reaction of the shrimps to these vibratory 
stimuli. Only when an animal was in close proximity (5 em. or less) 
to the source of the sound, or in contact with the walls of the vessel, 
would it respond, and then only feebly. Slight jarring of the aquarium 
produced no reaction, unless some part of the animal’s body directly 
touched the sides or bottom of the jar, or was in contact with the sound- 
producing instrument. 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 225 


The above experiments were duplicated on Crangon vulgaris with 
similar, though less marked results, as Crangon is much more sluggish 
than Paleemonetes. 

A third set of experiments was tried with Virbius zostericola, a 
shrimp-like decapod without otocysts. Normal animals responded vigor- 
ously on striking a glass jar partially submerged beneath the water in 
which they swam. This response, much increased by strychnine 
poisoning, was distinctly diminished when both antenne and antennules 
were removed. 

e. Meaning of these Experiments. All of my experiments confirmed 
the conclusion of Beer, that free-swimming decapods, whether possessing 
otocysts or not, will respond to stimuli which are transmitted to them 
by the liquid medium they inhabit. The next question is, to determine 
whether this response is caused by the perception of sownd waves or by 
the coarser vibrations or jars imparted to the water. In other words, 
have we to do with true audition or with the sense of touch? 

Beer has clearly shown that there is no such thing as the transmission 
of pure sound waves from air to water. Coarser waves are imparted to 
the liquid simultaneously with those of sound, and can readily be felt 
by the immersed hand. 

After making a number of trials with sounds produced as in the pre- 
ceding experiments, I ascertained that the vibrations not only could be 
plainly felt by the submerged hand, but also that they could be felt at 
a distance from 10 to 20 em. greater than that at which the shrimps would 
react. This fact does not at all prove that the animals experimented 
with do not hear, but merely shows that the responses supposedly pro- 
duced by sound stimuli may be simple tactile reflexes, called forth by 
vibrations which, since appreciable to the immersed fingers, we may cer- 
tainly assume to be felé by these animals, so well supplied with delicate 
tactile organs. 

That the reaction is really due to tactile stimulus rather than to audi- 
tion, is indicated by several facts brought out by the experiments : 

(1) Animals, when near the wall of the vessel, even though distant 
from the source of the sound, respond vigorously, leaping nway from the 
wall and toward the sound. The wall is set into vibration by the pro- 
duction of the sound, and it is apparently this vibration which affects 
them, rather than the true sound-waves imparted to the water. 

(2) The average distance from the source of the sound at which they 
will respond is less than that at which vibrations may be felt by the 
hand. 


226 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


(3) Removal of the antennz and antennules which are supplied with 
numerous tactile bristles, inhibits the reaction. 

(4) Decapods, such as Virbius, normally without otocysts respond 
vigorously ; but removal of antennz and antennules diminishes their 
sensibility in a marked degree. 

(5) Precisely the same responses as were called forth by the produc- 
tion of sound were also obtained by simply tapping or jarring the walls 
of the aquarium. 

Whether due to tactile stimulus or to audition, the fact remains, that 
the otocyst has little or no part in producing the reactions observed in 
the series of experiments; for (1) decapods normally without otocysts 
respond as vigorously to the same stimuli as those possessing them, and 
(2) the removal of the sacs from the latter has only a very slight in- 
hibiting effect, which might be due either to the loss of these organs, 
or to the injury of the nerves supplying the many tactile bristles of the 
antennule. 

Consequently, the otocyst not being the organ by stimulation of which . 
responses to sound vibrations are called forth, and there being no other 
sensory apparatus in Crustacea especially differentiated for the reception 
of sound waves, we are led to the conclusion that in decapod Crustacea 
a true auditory organ is wanting. 

The acute tactile sense of decapods may to some extent serve the 
same purpose that audition does in vertebrates. In mammals the senses 
of touch and hearing grade into each other. The range of the average 
auditory organ in mammals is from 30 to 16,000 vibrations per second ; 
waves of less than 30 vibrations per second do not usually produce audi- 
tory sensations, but are appreciable to the tactile sense. It is important 
to note that decapods respond most vigorously to low notes, and not at 
all to high notes or sounds produced by very rapid vibrations. This 
fact would seem to be good evidence that the vibrations imparted to 
the water and perceived by decapods correspond to those which produce 
tactile rather than auditory sensations in vertebrates. 


2. Responses of Gelasimus pugilator (Brachyuran decapod). 


a. To Vibrations transmitted to Water. On the conduction of sound 
waves to water by the same means as in the preceding experiments, these 
fiddler crabs responded, but by no means as vigorously as did the Ma- 
erura. They always rested upon the bottom of the aquarium, and 
reacted by retiring slowly, either from the source of the sound, or from 
the vibrating walls of the aquarium. In either case the response took 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. PAT 


place only when the animal was within a few centimetres of the vibrat- 
ing surface, and was most marked when the antenne and antennules 
were in close proximity to it. After blinding the animals and removing 
their otocysts, no apparent difference could be detected in the reactions 
called forth, as compared with those of normal crabs; removal of the 
first two pairs of appendages caused, on the contrary, the responses to 
almost completely disappear. 

b. To Atmospheric Sounds. As the fiddler crab is on land a large 
part of the time, a number of experiments were tried to determine the 
effect of aerial vibrations upon them when they were feeding under per- 
fectly normal conditions. A position for observation was selected near 
a bank which was completely honeycombed by their burrows, where 
one could see the animals perfectly well, and yet be screened from their 
view by intervening bushes. If one remained perfectly motionless, the 
animals would come within a short distance of the observer’s place of 
concealment, feeding as unconcernedly as if no one were near. Whena 
number of crabs were little more than five feet distant, a horn was blown, 
care being taken to direct it away from them. Although a sound was 
thus produced loud enough to be heard at some distance, all the animals 
continued to feed undisturbed. 

The striking together of two stones, and the sound produced by strik- 
ing an iron pipe with a stone (the objects in both cases being held in 
the hand) also had no effect upon them. On striking the ground with 
a heavy stone all the crabs within a radius of ten or twelve feet were 
startled ; some of them merely stopped feeding, while others scuttled 
into their burrows. The same result was brought about by simply 
stamping upon the ground. If a quick movement was made in the 
sight of the animals, they at once scattered precipitately to their holes. 
These observations were repeated a number of times, and on crabs of 
two different localities, with the same results. 

From these experiments and observations, we may draw the conclusion 
that the fiddler crab, whether in water or on land, does not respond to 
true sound-stimuli, but is affected only by jars or vibrations transmitted 
to the water or to the ground. In neither case can they be said to hear. 
When feeding upon land they do not depend upon an anditory sense to 
protect them from terrestrial enemies, but rely entirely upon their keen 
vision and delicate tactile organs. 

The statement is generally accepted, that all animals which produce 
sounds also have a sense of hearing, and this is advanced as an argu- 
ment in favor of audition in Crustacea. The two well-known examples 


228 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


of sound production among decapods, observed by T. Parker ('78) and 
Goode (’78), are (1) the stridulation of the rock lobster, Palinurus, where 
the sound is produced by rubbing the second segment of the antenna 
against the antennule, and (2) the pistol-like report produced by Alpheus 
in snapping together the claws of the great chela. As Beer has pointed 
out, the otocyst is poorly developed in Palinurus; furthermore, no in- 
dividuals of either species have ever been observed to respond in any way 
when these snappings or stridulations were produced. 

We can no more argue, from these two instances of sound production 
in decapods, that there is an auditory function in all Crustacea than 
we can that all fish hear because the drum-fish makes a sound. 

The enemies of water-inhabiting crustaceans produce no sounds 
which would reveal their presence to their prey; the latter would 
therefore have to rely upon other forms of stimulation for the detec- 
tion of their foes. Even if it were admitted that they possessed a sense 
of hearing, yet, as shown both by Beer’s experiments and by my own, 
it must be so restricted in range that they would be able to detect 
sound produced at no greater distance than that at which the vibra- 
tions could be felt by the hand. Such a dull sense as this would be 
of no practical value in protecting crustaceans from their foes. 

Both observation and experiment lead, then, to the following general 
conclusions : 

(1) The reactions formerly attributed to sound stimuli are nothing 
more than tactile reflexes. 

(2) The otocyst has little or no part in calling forth these reactions. 

(3) There is no direct evidence to prove that decapod Crustacea 
hear, and until such evidence has been obtained, we are not warranted 
in ascribing to the otocyst a true auditory function. 


II. The Otocyst as an Organ of Equilibration. 


All water-inhabiting, free-swimming animals which maintain a defi- 
nite position with reference to gravity either during locomotion or 
when at rest, can thus orient themselves only under one or the other 
of two conditions : 

Either the animal must be normally in a condition of stable equi- 
librium, keeping its definite position under the influence of gravity like 
any inanimate body; or, if a position of unstable equilibrium is main- 
tained, the animal must in some way be made sensible of the direction 
of gravity, and must keep itself in equilibrium by its own efforts. 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 229 


In the first case merely the mechanical action of gravity is called 
into play; in the second instance, besides the outside action of a 
physical agent, a subjective sense of direction and orientation is 
involved. 

In free-swimming decapods the body, moving or at rest, is in a 
position of unstable equilibrium. The dorsal side being always kept 
uppermost, the centre of gravity is high up, and a dead individual or 
an inanimate object of the same size, form, and disposition of weight 
would at once turn over. These animals must then by some means 
be rendered sensible to the direction of gravity, in order to be able 
to maintain a definite position of unstable equilibrium with reference 
to it. To determine what are the organs which perform the function 
of equilibration, the following means have been employed in the present 
investigation : 

(1) Removal, or prevention of the action of an organ, and observa- 
tion of the effects on the equilibration of swimming or walking decapods. 

(2) Observation of the effect of such removal on the gimbol-like 
movements of the eyestalks (compensation movements) when the 
animal is rotated about its different axes. 

(3) Observations on the orientation of animals normally without 
otocysts. 

(4) The effect of the development of the otocyst on the equilibration 
of the free-swimming larve. 

(5) The effect on equilibration of the addition of magnetic attraction 
acting on the otocyst at right angles to the pull of gravity. 

In these experiments blinding was accomplished by painting the 
eyestalks with a mixture of lampblack and shellac. The otocysts 
were removed under the lens of a dissecting microscope with the aid 
of a fine needle, bent in the form of a hook. Other parts, such as 
flagella of antennz and antennules, were simply cut off with a pair 
of fine scissors. Palemonetes vulgaris, being hardy, was the species 
chiefly employed, but experiments of a like nature were also carried 
on with Mysis, Crangon, and Gelasimus. A large number of trials 
were made with each species. When organs were cut off or destroyed, 
the animals so operated upon were kept under observation for from 15 
to 25 days, and the experiments were then repeated, in order to make 
sure that the effects observed directly after the operation were not due 
to abnormal conditions produced by nervous shock. 


VOL. XXXVI. — NO. 7 5 


230 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 


1. The Removal of Sense Organs and its Effect on Equilibration. 


The normal position in which a shrimp, like Palemonetes, holds 
itself while swimming, is very characteristic : 

(a) The dorsal side of the body is always kept uppermost, its dorso- 
ventral axis corresponding to the direction of gravity, and its long axis 
usually lying in a horizontal plane. 

(6) Shrimps can be overturned only with difficulty, and even if this 
is accomplished, they right themselves at once. 

(ec) Animals coming to rest upon surfaces not horizontal tend to 
keep themselves in the horizontal plane, but with the dorsal side 
always up. 

a. Eyes blinded. Nearly fifty animals were operated upon in this 
way and their movements observed. Placed in an aquarium, they swam 
about indiscriminately, but always with the dorsal side up, there being 
little if any rolling from side to side. They were not easily overturned 
artificially, and when interfered with, righted themselves quickly. The 
most noticeable difference to be observed between their mcevements 
and those of normal animals was the tendency to remain quiet and 
to hold fast to any object with which they came into contact, thus 
substituting the sense of touch for that of vision lost. It is apparent, 
therefore, that some organ or organs other than the eyes play the chief 
part in equilibration. 

b. Both Otocysts removed. Twenty-five animals were operated upon 
by removing both otocysts. In swimming there was still a strong 
tendency to keep the dorsal side uppermost, but there was in every 
case marked rolling from side to side, which occasionally culminated 
in a complete rotation about the long axis of the body. The animals 
could be easily overturned, and though they strove to right themselves, 
it was not accomplished as soon nor as accurately as in normal or blinded 
shrimps. They were more apt to remain quiet, or to swim along upon 
the bottom of the aquarium, than to swim free. If the long flagella 
of the first and second antenne were removed, rolling motions were 
increased and also the difficulty in righting themselves if overturned, 
the flagella being probably used ag balancing organs in equilibration ; 
but the extirpation of the otocysts alone brings about a marked loss of 
orientation, much more pronounced than that produced by simply 
blinding. 

c. Both Eyes blinded and both Otocysts removed. Upon removal 
of both otocysts and blinding of both eyes, entire loss of the normal 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. Dol 


position in swimming resulted in twenty-one trials out of the twenty-five 
made. The animals turn over and over, rotating about the long axis, 
now in one direction, now in the other; they also pitch forward and 
backward about their transverse horizontal axis, and often swim upon 
their backs. They do not resist overturning, unless holding to some 
stationary object, and make no attempt to right themselves when swim- 
ming free. The moment they come in contact with a horizontal sur- 
face, such as the bottom of an aquarium, they at once take up their 
normal position, righting themselves quickly, but if the surface they 
touch be oblique or vertical, and even if they come in contact with 
the under side of a horizontal surface, they cling to it tenaciously, 
taking up a position with reference to the plane of contact, and not in 
relation to the direction of gravity, as is the case with normal ani- 
mals. Thus the phenomena of orientation completely disappear in 
the majority of cases when both otocysts and eyes are rendered func- 
tionless, at least in the free-swimming animal. When the animal 
comes in contact with solid objects, the sense of touch asserts itself 
and the phenomena of orientation are again, to a certain degree, made 
manifest. 

d. One Eye blinded, both Otocysts removed. The conditions here 
are essentially the same as when only the otocysts are extirpated. 
There is a well-defined rolling motion in swimming, and if overturned 
artificially, the animal is very slow in regaining the original position. 

e. Both Eyes blinded, one Otocyst removed. In such experiments 
no effect was produced different from that brought about by blinding 
alone. There was no evidence of a tilting of the dorso-ventral axis 
toward the injured side, as might be expected, if the functions of the 
two otocysts were co-ordinated. Nor was there during swimming 
a rotation toward the side from which the otocyst had been re- 
moved. We may therefore conclude that in the phenomena of equi- 
libration each otocyst, as well as each eye, acts independently. 

As check experiments, both antennules were removed distal to the 
otocysts. No abnormal conditions were produced in swimming move- 
ments, the wounds healed, and these individuals lived in aquaria as 
long as normal animals. Where the otocysts were extirpated, individ- 
uals were kept as long as four weeks, and after this interval, when 
blinded, they gave the same evidences of loss of orientation as they did 
immediately after the operation. 

These observations, made upon Palezemonetes, were found to hold true 
also for Crangon, Mysis, and lobster larve. Experimentation with the 


2am BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


fiddler crab gave like results. If blinded and deprived of otocysts, the 
erabs rolled both forward and backward when walking or running; 
this effect was still more apparent when the animals were placed in the 
water. : 


2. Removal of Sense Organs and its Effect on the Compensation 
Movements of the Eyes. 


The following experiments, carried out on Gelasinus pugilator, confirm 
the work done by Clark (96). When a crab is tilted to the right or 
left, forward or backward, the eyestalks tend to keep their original direc- 
tions, thus seemingly moving through a certain angle. Such move- 
ments, which have been observed also for the head and eyes of many 
vertebrates and insects, are called compensation movements, and the 
angle of movement, the angle of compensation. 

The angle of compensation in the fiddler crab was measured by means 
of the apparatus described by Clark (’96), a small table to which the 
animals could be securely fastened and tilted about their chief horizontal 
axis. A scale ruled to degrees enabled one to read accurately the angle 
of compensation, and the angle through which the animal was turned. 
The long eyestalks of the fiddler crab make it easy to determine the 
angle of the eye movements. 

The angle through which the animals were turned was in all cases 
45° first to the right, then to the left, about the chief, or longitu- 
dinal axis of the body. In each experiment fifty animals were used, the 
average being taken as the angle of compensation. These animals were 
most of them kept twenty days, and the angle then measured again, 
thus guarding against abnormal conditions. 

a. Normal Animals. In normal crabs the eyestalks are so held as to 
make an angle of about 22° with the vertical. The eye movements are 
always correlated, and if the animal’s body is tilted to the right (45°) 
the right eye makes a compensating movement of 18° upward, the left 
eye one of 25° upward; rotated to the left, the conditions are just re- 
versed, the right eye now moving through an angle of 25°. The move- 
ment of the eye of the side toward which the animal is rotated is in 
each case less by about 7° than that of the other eyestalk. This is due 
to interference of the carapace with the eyestalk, preventing its passage 
through a greater angle. 

b. Both Eyes blinded. Tilting either to right or left had the same 
general effect as in normal animals, but the right eye described an arc 
of only 13°, the left eye one of 20°, or vice versa. There is thus a 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 233 


marked reduction in the angle of compensation, a decrease of about 5°, 
as compared with normal animals. This shows clearly the extent to 
which vision enters into the orientation of these animals. 

c. Both Otocysts removed. The angle of compensation is here reduced 
to 3° and 5°, respectively, for the eyestalks on the side toward and from 
which the rotation takes place. Even without rotation the positions in 
which the eyes are held are not definite, as they are in animals which 
possess otocysts. The stalks often make an angle of 40° or more with 
the vertical, and their movements are no longer correlated. This, 
together with the marked decrease in the angle of compensation, as 
compared with that of blinded animals, makes it evident that in 
equilibration and orientation the otocyst plays a much more impor- 
tant part than does the organ of vision. 

d. Both Eyes blinded and both Otocysts removed. On rotation it was 
found that the compensatory movements of the eyestalks were practically 
wanting. ‘Two individuals only out of fifty showed movements of from 
3° to 5°. In the greater number of cases no movement could be de- 
tected, and in the remainder the angle averaged lessthan 1°. There was 
a still greater tendency for the eyestalks to be held in indefinite positions 
when at rest, and at unequal angles. Fifteen such individuals were kept 
in an aquarium more than twenty days, and after this lapse of time 
practically the same results were obtained, showing that the shock of the 
operation of removing the otocyst had no effect upon the results of the 
experiments. Furthermore, removal of the antennules distal to the oto- 
cysts had absolutely no inhibiting effect upon the movements of the 
eyestalks. 

This series of experiments corroborates, as far as they go, the conclu- 
sions of Clark (96). It is clear from them that the otocyst is the chief 
organ in equilibration, though sight also plays an important part in the 
orientation of these animals. 

Since the above work was done (July, 1899) a paper has been pub- 
lished by Lyon (99) on the comparative physiology of compensatory 
movements. These movements were studied by him in many vertebrate 
and invertebrate forms; they were found to exist in insects as well as 
Crustacea. Using the crayfish, he confirms Clark’s results to some extent, 
but finds that on blinding the animals and removing the otocysts a con- 
siderable angle of compensation still persists. This, together with the 
fact that insects, which lack otocysts, show the characteristic movements, 
he uses as an argument against the otocyst being an organ of equilibra- 
tion. Lyon also finds that upon rotation about a vertical axis there isa 


bo 


34 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


compensation movement of the eyestalks of the normal crayfish through 
an angle of 10° to 18° ; and, further, that when the animal is rotated 
about its long axis blinding causes a diminution of 10% in the angle of 
compensation. His results therefore give a much more important place 
to vision in orientation than do the conclusions of Clark and myself. 
However, from the combined results of the experiments of Clark, Lyon, 
and myself, one cannot avoid the conclusion that, in the fiddler crab at 
least, the otocyst is by far the most important organ in equilibration ; 
next in order comes vision, and then muscular and tactile sense. 


3. Lquilibration of Animals normally without Otocysts. 


Virbius zostericola, a shrimp quite common at Wood’s Hole, Mass., 
does not possess otocysts. Observation and experiment brought out 
several interesting facts concerning it. In the first place, it is not a free- 
swimming form. Its normal habitat is on the eel grass, to which it 
clings in positions indifferent to the direction of gravity. When forced 
to swim, it does so in a very uncertain manner, with the dorsal side usu- 
ally uppermost, though this is a position of unstable equilibrium. If 
overturned artificially (and this is easily accomplished), it rights itself 
slowly and will cling to the first object it may chance to touch. Re- 
moved from its supporting blades of eel-grass, its unstable manner of 
swimming closely resembles that of shrimps in which the otocysts have 
been destroyed. If the eyestalks are painted with lampblack, and the 
animals so treated are placed in a large aquarium, and forced to swim, 
apparently all sense of direction and means of orientation are lost. 


4. The Effect of the Development of the Otocyst on the Equilibration of 
Lobster Larve. 


As has been shown in the morphological part of this paper, there is no 
otocyst in the newly hatched larva of either Palemonetes, the lobster, 
or the crab, nor is there a functional organ during the first three larval 
stages. It begins to invaginate only in the second larval stage, and it is 
merely a shallow cup-like depression in the third stage; not until the 
next moult do the sensory hairs and otoliths appear. 

When we examine the conditions as to equilibration and manner of 
swimming in the different larval stages, we find that in the first larva 
the body is not definitely oriented while swimming. Newly hatched 
lobsters are very unstable in their movements, often swim or come to rest 
upon their backs or sides, and show a tendency to roll from side to side 
while swimming. The animal swims by means of the exopods of the 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 235 


thoracic appendages; the abdominal segments are flexed ventrally, and 
the thoracic endopods, hanging down, steady the rolling motions some- 
what. In the second stage the conditions are essentially the same. 

In the third stage the larve are more stable, though the otocyst 
is still functionless. This greater stability is explained when the 


Figure B. 


Lateral view of lobster larva of the third stage, showing swimming position. 
Magnified 6 diameters. 


swimming position of the body and appendages is observed (Fig. 5). 
The thoracic appendages are now relatively large, as compared with the 
size of the body. They are allowed to hang down ventrally, and in 
conjunction with the curved condition of the abdominal segments, serve 
to lower the position of the centre of gravity in the whole animal, thus 
rendering its swimming position much more stable. 


Figure C. 


Lateral view of lobster larva of fourth stage, illustrating the change in swimming position 
due to the presence of a functional otocyst. Magnified 6 diameters. 


Turning now to the fourth larval stage, we find the swimming posi- 
tion of the body entirely changed (Fig. C). The abdomen is no longer 
flexed and curved ventrally, but is held in approximately the same 
horizontal plane as the cephalothorax, while the thoracic appendages, 
instead of dragging downward through the water, are held up and for- 
ward in a line parallel with the long axis of the body. The great chelz 
project in front like the arms of a person preparing to dive, the exopods 


236 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


of the thoracic appendages have been lost, and the larve now swim 
swiftly by means of the abdominal swimmerets. 

Although, from the position in which the body and appendages are 
held, the larva is in unstable equilibrium, it now orients itself very 
definitely during locomotion, in sharp contrast to the preceding stages. 
All signs of rolling from side to side, or pitching forwards, are com- 
pletely lost. The larva swim straight ahead with the body held 
usually in a horizontal plane and dorsal side up. The same position is 
also invariably maintained when the animals come to rest. 

Thus this sudden change as to form and swimming position in the 
fourth larva, unfavorable though it is for equilibration, is yet accom- 
panied by more delicate powers of orientation, and greater stability in 
swimming than are met with in the three earlier stages, where the 
centre of gravity of the animal is lower. Bearing in mind the fact that 
the otocyst first becomes functional in the fourth larval stage, we can 
only conclude that an intimate connection exists between its appearance 
as an active organ, and the delicate static sense which is suddenly 
exhibited by the larvee. 

If larve of the first, second, and third stages are blinded, their 
powers of orientation are almost entirely lost, but the same experiment 
has little or no effect upon the equilibration of the fourth larva. The 
first three stages thus depend mainly on vision for their imperfect ori- 
entation ; in the next stage this function has been largely transferred 
to the otocyst. 

A similar correlation between the development of the otocyst and the 
appearance of a static sense is found in the metamorphosis of the crab. 
The pelagic unstable Zoea larva is without otocysts, while the Megalops 
larva, which exhibits perfect powers of equilibration, possesses these 
organs well developed, and even containing otoliths, which are absent 
in the sac of the adult. 

The correlation which evidently exists between the formation of the 
functional otocyst and the sudden increase in static powers exhibited 
by lobster larvee is particularly well shown in the marked alteration in 
the swimming position maintained by the fourth larva, as compared 
with that of the three earlier stages. Previous to the fourth stage, the 
lack of a delicate static organ is compensated for by the maintenance 
of an attitude in swimming which increases the stability of the moving 
body. Just as Bethe (95) found that Mysis, deprived of its otocysts, 
would after an interval of some days recover its power of orientation by 
curving the abdomen upward and thus. by lowering the centre of gravity, 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 237 


put the body in natural equilibrium, so in the case of the first three 
lobster larve, the attitude maintained is an adaptation for the greater 
stability of the free-swimming animal, as yet without static organs. 
But when, in the next stage, the otocyst becomes functional, such an 
adaptation is no longer necessary, and the sudden change to the un- 
stable swimming position of the fourth larval stage results (Fig. C). 
This is the more natural attitude, and is advantageous to the animal 
in that it allows of greater speed in swimming. 


5. The Funetion of the Otoliths. 


At the time when the otocyst was regarded as an auditory organ, the 
otoliths were supposed to act simply as intensifiers of the sound vibra- 
tions, but viewing the sac as a static organ, the role played by the 
otoliths must assume a different aspect. The fact that they are want- 
ing in the Brachyura, which nevertheless exhibit strong powers of 
orientation, might be used as an argument against their playing any 
important part in equilibration, But as they are present in the larval 
crab, and as they disappear only when the otocyst becomes highly 
differentiated, and when sensory hairs much more delicately constructed 
than the otolith bristles are developed, this argument loses most of its 
weight. 

For determining the functions of the otoliths two methods may be 
employed: (a) Observing the effect on equilibration and orientation 
following the removal of the otoliths, or the prevention of the normal 
process of taking them in after ecdysis. (6) Substitution of iron dust 
or iron filings for the otoliths, and the employment of an electro-magnet 
to modify the action of gravity. If the otoliths are static in function, 
the animals should orient themselves with reference to the resultant of 
the attraction of the magnet, and the pull of gravity. 

The first of these methods was attempted by Kreidl (’94), but failed, 
as he was unable completely to remove the otoliths. His results with 
the second method of experimentation were definite and affirmative. 
Lyon (99) attempted to repeat and verify Kreidl’s work, but his experi- 
ments were incomplete and negative in their results. 

Otoliths, always normally present in macruran decapods, are lacking 
for only a short time after ecdysis. So short indeed is this interval, 
that it is extremely difficult to find otocysts of newly moulted animals 
which are without otoliths. Nor is it usually possible to prevent a 
crustacean which has been observed to cast its test, from getting new 
otoliths into the sac ; at least not for a sufficiently long period to allow 


238 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 


the animal otherwise to regain its normal condition. Even if placed at 
once in filtered water, some otoliths soon make their appearance, probably 
originating from the excreta of the animals themselves. 

In lobsters the larve regain their normal condition within a much 
shorter interval after ecdysis than do adult individuals ; their digestive 
tract is also much less likely to contain material suitable for the forma- 
tion of otoliths. Therefore, after trying in vain to completely remove 
the otoliths from the sacs of Crangon and Palemonetes, my attention 
was directed to lobster larvee as much more favorable material than 
the adult shrimps. As they moult at intervals of a few days, it is also 
much easier to obtain them directly after ecdysis or in the very act 
itself. So obtained, and placed at once into filtered sea water, larve of 
the fourth stage may be kept without otoliths for from twenty-four to 
forty-eight hours, and a favorable opportunity is thus given for observing 
the effect produced, by the lack of otoliths on the equilibrium of the 
animals. 

Observations were made on eighteen larve of the fourth and fifth stages, 
all of them being kept free from otoliths for at least twelve hours. Within 
two hours after moulting most of them swam about actively, and ate 
greedily when fed with bits of crab’s liver. In swimming, however, they 
show distinctly the phenomena manifested by shrimps which have been 
deprived of their otocysts. There is both “rolling” from side to side, 
and ‘“ pitching” forward and backward; often they swim with the 
ventral side uppermost. Much more easily overturned than normal 
larvee, they do not right themselves at once, but if turned upon the 
back, will continue to swim in that abnormal position. If blinded, 
the loss of equilibrium is still more marked. All these conditions 
are in strong contrast to the actions of the normal free-swimming larve 
of these stages, which conduct themselves in the characteristic manner 
already described for Paleemonetes. 

The observations having been made and recorded, the animals were 
killed, and the otocysts dissected out and examined under the micro- 
scope. Scarcely a particle of inorganic matter was found in the sacs 
of sixteen larve. In two individuals a few small grains of sand were 
found in one otocyst, but the other was entirely destitute of otoliths. 

From the number of cases observed it seems safe to conclude that the 
otoliths do play an important part in equilibration, and that it is the 
pull of gravity upon them which stimulates the sensory hairs of the sac. 
If the loss of the power of accurate orientation were to be attributed to 
the abnormal conditions resultant upon ecdysis, it might be said in 


a 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 259 


reply that the larve were perfectly normal when observed, as far as 
feeding and active swimming were concerned, and furthermore that the 
loss of equilibration disappeared at once when a larva without otoliths 
was allowed to obtain them. The results of these observations are 
also confirmed by the following experiments. 

The otoliths were removed from the sacs of Palemonetes by lifting 
the lid which covers the aperture, and forcing a fine jet of water into the 
cavity. Most of the sand having Leen thus washed out, the animals 
were placed in an aquarium upon the floor of which iron filings had been 
scattered and were allowed to remain until the iron particles had been 
taken into the sac in place of grains of sand. As an electromagnet, a 
steel bar 8 inches long and one quarter of an inch square was used. 
This was ground down nearly to a point at one end; about the other 
end were wound many layers of fine copper wire, the termini being 
connected with the circuit of a small six-celled battery. The shrimps 
employed in the experiments (Palzmonetes) were blinded by the usual 
method, — painting the eyestalks with a mixture of lampblack and 
shellac. The pointed end of the magnet was held about 3 cm. from the 
otocysts, at one side of and a little ventral to them. Animals with 
normal otoliths, if blinded, do not respond at all, and are apparently 
unaffected by the proximity of the magnet; they keep their normal 
position, dorsal side up, with the sagittal plane of the body coincident 
with the direction of gravity. If not blinded, they simply move slowly 
away from the magnet when it approaches too near. When, however, 
the magnet is brought into close proximity to otocysts containing iron 
filings, the dorsal side of the animal is turned, not toward the magnet, 
as might be expected if the changed position were due directly to the 
action of the magnet on the iron filings, but away from it. If the 
magnet was changed to a position on the other side of the shrimp, the 
turning was in the opposite direction, still away from the source of 
attraction. 

The above reaction was distinctly noted a number of times for each of 
the six animals experimented upon. As Kreidl’s work was fairly com- 
plete, only one series of experiments was tried in confirmation of his 
results. When the observations had been completed, the antennules of 
the six shrimps were removed and the otocysts examined under the 
microscope. In each case particles of iron were found nearly filling 
the sac, and if a magnet was held close to one of the latter, the whole 
antennule was lifted by the attractive force, showing clearly that there 
must have been an effective magnetic pull upon the otoliths of the live 


240 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


animals during the experiments. I believe there is only one explanation 
for this turning of the body away from the attracting force, and that is 
avery simple one. Under normal conditions the body of the shrimp 
is oriented with reference to gravity, and its dorso-ventral axis ap- 
proximately corresponds to the direction of this force. If the shrimp 
rotates around its chief axis either to right or left, say 90°, the direc- 
tion of the pull of gravity on the otoliths is at once changed, and through 
the medium of the latter other sensory hairs of the sac are stimulated. 
As a result, the shrimp turns back in a direction opposite to that in 
which it was rotated, until it is again in a normal relation to the 
direction of gravity. The employment of the magnet has no other 
effect than merely to change the direction of the orienting force. This 
is now no longer that of gravity alone, but the resultant of the two com- 
ponent forces, gravity and the pull of the magnet. The animal now 
maintains its swimming position in reference to this new line of attrac- 
tion, its dorso-ventral axis coincident with that line, and as a result the 
dorsal side is turned away from the magnet. To put it in another way, 
when the magnet is held close to the right side of the otocyst, the 
animal is stimulated precisely as it would be if rotated to the right 
45°, and it responds as it would normally in righting itself, i. e., by 
turning its body in the opposite direction through an angle sufficient 
to make its dorso-ventral axis coincide with the direction of the attrac- 
tive force ; in this case through an angle of 45°. 

This single series of observations completely confirm, as far as they 
go, the very important conclusions of Kreidl. The otoliths are found 
to play an important part in the functional activities of the otocyst, and 
the latter is conclusively proved to be a static organ, acted upon by the 
force of gravity; this force makes itself felt chiefly through the medium 
of the otoliths, and if they are absent, as described in a preceding set of 
experiments on lobster larvee, the function of the otocyst in Macrura 


i* 


is seriously impaired. 
6. The Function of the Hairs of the Otocyst. 


The function of the otocyst hairs of macruran decapods which are in 
contact with otoliths has been already briefly discussed in the first part 
of this paper. The stimulus imparted to the hair shaft through the 
medium of the otoliths makes itself most strongly felt at the labile base 
of the hair, owing to the rigidity of the shaft and the delicacy of the 
attaching membrane. At this point, too, the nerve fibre invariably ends, 
and the stimulus is thus transmitted to it, and at once carried to the 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 241 


brain. In the case of adult Brachyura, however, there are no otoliths 
in contact with the hairs of the otocyst, consequently the effect of 
gravity, if not entirely null, must be at least greatly lessened, unless 
indeed the hairs are so differentiated as to be themselves stimulated 
by it. 

Bethe (’97), acting on the idea that in tilting the animal the differ- 
ence in the pressure of the water might affect the hairs of the otocysts, 
placed crabs under very high pressures where the slight difference brought 
about by tilting would be practically eliminated. But he found that all 
the phenomena of equilibration still persisted. 

It is probable that in the otocyst of Carcinus the thread hairs are the 
most important sensory organs of the sac. The hook hairs, originally 
in the larva attached to otoliths, later, with the loss of the sand granules, 
lose much of their functional activity ; the third group of hairs can- 
not be of great importance, as I could not demonstrate satisfactorily 
their nerve connections, and their structure alone is such as to preclude 
their being affected by very delicate stimuli. The thread hairs, how- 
ever, in both structure and position are fitted for the fulfillment of such 
a function as has been ascribed to them. The shaft is long, attenuate, 
only slightly fringed at the tip, and attached at the base by a very thin 
membrane, which allows free movement to the rigid shaft about this 
region as upon a joint. I have observed in studying freshly dissected 
otocysts that a slight tilting of the watch glass in which they were con- 
tained caused these hairs to sway extensively. 

From Clark’s experiments and my own, it was apparent that upon 
rotation in a horizontal plane, there was little or no compensatory 
movement of the eyestalks, and that when there is such a reaction, the 
angle of compensation is not maintained, but the eyes return at once to 
their original positions. Also, on rotation about the animal’s lateral 
axis, the angle of compensation is not as great, when the rotation is 
rapid and jerky, as when performed slowly and smoothly. These two 
facts preclude the possibility of the hairs being affected by movements of 
the fluid surrounding them, at least to any great extent. For if they 
were so affected, the angle of compensation should be the same, in what- 
ever plane the animals are rotated, and the position of the eyestalks 
should be in every case maintained by compensation movements. 

There still remain two ways in which the hairs may be so affected as 
to bring about nervous stimulus. Either they may be lighter than the 
surrounding fluid, and consequently tend always to float erect, no matter 
what position the otocyst may take relative to them; or they may be 


bo 


42 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


heavier than the liquid contents of the otocyst, in which case they would 
be affected by gravity directly, and exposed to a greater or less pull 
according to their different positions in the sac. My observations made 
on dissections of fresh material of both young and adult crabs, do not 
confirm the first of these hypotheses. The hairs rarely, if ever, float 
upright in the fluid of the otocyst ; on the contrary they usually project 
out horizontally, with their tips a little lower than their bases; and 
such conditions would favor the second supposition, that they are heavier 
than the surrounding fluid. Unfortunately, when fresh material was at 
hand, my attention was directed toward other problems, and no dissec- 
tions or observations were made with the settlement of this question 
primarily in view. It is, however, a point well worth future experimenta- 
tion, for the function of these hairs is apparently similar to that of the 
auditory hairs of the vertebrate criste acustice, and to clearly show how 
they are stimulated would throw light on an important problem in the 
physiology of the vertebrate ear. 


SUMMARY. 


1. The cuticular lining of the otocyst, found in the basal segment of 
the antennule of all decapod Crustacea, is cast with the test at each moult. 
It is composed of thin chitin, and is suspended from the dorsal wall of 
the antennule, which presents an aperture in Macrura, in the larval stages 
of Brachyura, and also in adult Brachyura directly after ecdysis. 

2. In Macrura a single sensory prominence is present, either on the 
floor or sides of the sac. In Brachyura there are three sensory regions. 
The sensory hairs are borne upon these cushions, usually in curved rows. 

3. The otolith hairs are heavily fringed, often bent or hooked. In 
Macrura they are attached to the wall of the sac by a thin bulb of 
chitin; in Brachyura the base of the hair shaft is inserted into a cup- 
like depression ; both methods of attachment allow the hair to sway 
freely upon its base. 

4. The free hairs of the otocyst, found in the lobster and all Bra- 
chyura, are extremely long and attenuate ; their basal attachment is deli- 
cate, and renders them much more sensitive than the otolith hairs. 

5. All sensory hairs are formed as double-walled tubes by numerous 
matrix cells situated beneath the hypodermis, from which they originate. 
After ecdysis processes from these cells extend into the shaft of the 
newly formed hair. In preparation for the next moult these processes 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 243 


are withdrawn, the matrix cells recede from the base of the old hair, and 
arrange themselves about the nerve fibre for the formation of the new 
bristle. There is a period between moults, more or less extended, dur- 
ing which no living substance is present in the greater part of the cavity 
of the hair. 

6. The otoliths are grains of sand taken in from the exterior (first, in 
the case of the lobster, by the fourth larva) and renewed after each 
moult ; they may lie free in the otocyst, or be attached to the sensory 
hairs. In Brachyura they are found only in the Megalops stage. 

7. Glands similar in structure to the tegumentary glands are present 
in the lobster and crayfish beneath the sensory cushions which bear oto- 
lith hairs. They secrete a substance for the attachment of the otoliths to 
the pinnules of the bristles. 

8. The innervation of the otocyst hairs and olfactory bristles is dis- 
tinctly unlike. 

(a) The otocyst hairs have each a single nerve element, and the 
terminal fibre ends in the enlarged base of the shaft without branching. 

(6) Each olfactory bristle is innervated by numerous ganglion cells 
(100 or more). The peripheral strand of fibres from these cells extends 
some distance into the cavity of the hair, terminating free and without 
modification of any kind. 

9. The central terminations of all the otocyst fibres are in two closely 
connected neuropilar masses at the posterior end of the brain, median 
to those of the second antennz, and ventral to the optic centres. The 
nerve sheaths disappear as the fibres enter the “ Punktsubstanz,” and 
the fibrilla soon separate. They cannot be traced to determinate 
endings, nor are they ever directly connected centrally, with ganglion 
cells. 

10. Each sensory nerve fibre is composed of numerous fibrille, 
embedded in a semi-fluid ‘‘ perifibrillar” substance, which in turn is 
surrounded by a delicate sheath. The flowing together of the peri- 
fibrillar matrix causes the beaded or varicose appearances characteristic 
of methylen blue, and silver impregnations. The fibrillar structure can 
be demonstrated in both the central and peripheral portions of the 
fibres. 

11. The sensory ganglion cells are all typically bipolar and elongate 
in form. They are placed at some distance from the base of the hair 
which they supply, and show no fibrillar structure. 

12. In the shrimp-like decapods, such as Paleemonetes and Crangon, 
a nucleated myelin sheath surrounds each sensory fibre and ganglion 


244 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


cell, extending from the neuropil of the brain nearly to the peripheral 
ending of the fibre. 

13. Each sensory ganglion cell with its central and peripheral fibres 
constitutes a single nervous element or neuron. ‘The neurons are 
trophic units, and direct connection between two neurons was not 
demonstrated. 

14. In those decapods which pass through free-swimming larval 
stages, the otocyst develops as an invagination of the dorsal ectoderm 
of the basal segment of the antennule, and becomes functional only at 
the fourth moult after hatching. 

15. Invagination begins at the second larval stage, but the matrix 
cells which are to form the sensory hairs of the sac, make their appear- 
ance in the first larva, being derived from the cells of the hypodermis. 

16. During the third stage the sensory hairs are formed below the 
floor of the shallow sac; at the next moult these become functional, 
the sac enlarges, and otoliths make their appearance. The otocyst 
is now functional, the hairs are innervated as in the adult, and more 
than 100 of them may be present. After the fourth stage the chief 
changes are the increase in the number of otocyst hairs, and the gradual 
constriction of the orifice of the sac. 

17. In Brachyura the Zoea larva is without a functional sac. In the 
Megalops the otocyst is open, and contains numerous sensory hairs and 
otoliths. During the next two stages the aperture closes and takes on 
the adult condition, without otoliths. 

18. Structurally, the otocyst of decapods may be compared roughly 
to the utriculus of such a vertebrate as Myxine; the sac of Paleemonetes 
to a single isolated ampulla, and its sensory cushion to a crista 
acustica. The closed otocyst of Brachyura has three sensory regions 
and is without otoliths. It therefore approaches in general structure 
the utriculus of the higher vertebrates. Each sensory element of the 
otocyst is comparable to a single sensory component in the vertebrate 
crista. In each there is a modified organ for the reception of stimuli, 
connected basally with the terminal fibre of a sensory neuron. 

19. There is no part of the decapod otocyst which is structurally com- 
parable to the middle ear, semi-circular canals, or cochlea of vertebrates. 

20. There is no direct evidence to prove that decapod Crustacea react 
to true sounds produced either in water or in air. The reactions 
formerly attributed to audition are probably due to tactile reflexes. 

21. The otocyst plays little or no part in calling forth these reac- 
tions, and does not function as a true auditory organ. 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 245 


22, Equilibration is made possible by three sets of organs, the oto-/ 
cysts, the eyes, and the tactile bristles. 

23. In free-swimming decapods the otocyst is by far the most im- 
portant of these static organs functionally, vision being secondary to it. 
Four facts go to prove this: 

(a) The removal of the otocysts causes a much greater loss of power 
of orientation, and a greater decrease in the compensatory movements 
of the eyestalks, than the loss of vision. 

(6) Decapods and Entomostraca normally without otocysts either 
swim in unstable equilibrium, or in a position identical to that which 
an inanimate object of the same form and weight would take under 
the influence of gravity. 

(c) Lobster larvee without functional otocysts are unstable in their 
swimming movements, but orient themselves with great accuracy at 
the stage when the sac becomes an active sense organ. 

(d) If iron filings are substituted for the otoliths, and an electro- 
magnet is employed to modify the effect of the pull and direction of 
gravity, shrimps orient themselves with reference to the direction of 
the resultant pull of the two forces, precisely as they do to the 
attraction of gravity alone. 

24. In lobster larvee of the third and fourth stages there is a direct 
correlation between the metamorphosis of the otocyst from a func- 
tionless to an active organ, and the changes in the swimming position 
of the animal. When the sac is inactive (third stage), the swimming 
position of the body and appendages is an adaptation which places the 
larve in comparatively stable equilibrium. As the otocyst becomes 
functional (fourth stage), this adaptation is no longer necessary, and 
a much less stable position is maintained, but one more favorable for 
rapid locomotion. 

25. The otoliths in Macrura and larval Brachyura are the means 
by which the pull of gravity is transmitted to the hairs of the otocyst. 
On their complete removal there is loss of equilibration and power 
of orientation ; if iron filings are substituted for them, shrimps may 
be made to respond to the attraction of an electromagnet. 

26. In adult Brachyura otoliths are normally lacking. The otolith 
hairs have become practically functionless, and the thread hairs are 
modified in such a way as to make them directly responsive to the 
attraction of gravity without the aid of the otoliths. 


VOL. XXXVI. — NO. 7 6 


246 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


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animaux. ‘TT. 1-14, Paris. 
Minasi, A. 
1775. Dissertazione seconda su de’ timpanetti dell’ udito scoverti nel gran- 
chio paguro, e sulla bizzarra di lui vita. 136 p. Napoli. 
Morrill, A. D. 
98. The Innervation of the Auditory Epithelium of Mustelus canis, De Kay. 
Jour. Morph., Vol. 14, pp. 61-82, Pls. 7-8. 
Miiller, J. 
°37. Handbuch der Physiologie des Menschen. Bd. 2, Coblenz. 
Parker, G. H. 
°90. The Histology and Development of the Eye in the Lobster. Bull. Mus. 
Comp. Zool., Vol. 20, No. 1, pp. 1-60, Pls. 1-4. 
Parker, T. 
°78. Note on the Stridulating Organ of Palinurus vulgaris. Proc. Zool. Soc. 
London, 1878, pp. 292; 442-444, Pl. 30. 
Rath, O. vom. ’ 
’°87. Ueber die Hautsinnesorgane der Insecten. Zool. Anzeiger, Jahrg. 10, 
pp. 627-631, 645-649. 
Rath, O. vom. 
°88. Ueber die Hautsinnesorgane der Insekten. Zeitschr. f. wiss. Zool., Bd. 
46, pp. 413-454, Taf. 30-31. 
Rath, O. vom. 
°91. Zur Kenntniss der Hautsinnesorgane der Crustaceen. Zool. Anzeiger, 
Jahre. 14, pp. 195-200, 205-214. 


250 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


Rath, O. vom. 
°94. Ueber die Nervenendigung der Hautsinnesorgaue der Arthropoden nach 
Behandlung mit der Methylenblau- und Chromsilbermethode. Berichte 
Naturf. Gesellsch. Freiburg, Bd. 9, Heft 2, pp. 1-28, Taf. 2. 
Reichenbach, H. 
°86. Studien zur Entwicklungsgeschichte des Flusskrebses. Abhandl. 
Senckenberg. naturf. Gesellsch. Frankfurt a. M., Bd. 14, 137 p., 14 Taf. 
Retzius, G. 
°90. Zur Kenntniss des Nervensystems der Crustaceen. Biol. Untersuch., 
Bd. 1, pp. 1-50, Taf. 1-14, Stockholm. 
Retzius, G. 
°92. Ueber die neuen Prinzipien in der Lebre von der Einrichtung dee 
seusiblen Nervensystems. Biol. Untersuch., Bd. 4, pp. 49-56, 9 Figg. 
Stockholn. 
Retzius, G. 
°94. Zur Entwicklung der Zellen des Ganglion spirale acustici, und zur En- 
digungsweise des Gehornerven bei den Saigethieren. Biol. Untersuch., 
Bd. 6, pp. 52-57, Taf. 24-25. 
Retzius, G. 
°95. Das sensible Nervensystem der Crustaceen. Biol. Untersuch., Bd. 7, 
pp- 12-18, Taf. 4-6. 
Rosenthal, C. 
"11. Ueber die Geruchssinne der Insecten. Reil’s Arch. f. Physiol., Bd. 10, 
pp. 427-439, Taf. 8. 
Sars, G. O. 
°67. Histoire naturelle des crustaces de l’eau douce de Norwége. ii+145 p., 
10 pls. Christiana. 
Siebold, C. T. von. 
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Jahrg. 10, Bd. 1, pp. 52-81, Taf. 1. 
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Souleyet. 
43. Observations anatomiques, physiologiques, et zoologiques sur les mol- 
lusques ptéropodes. Compt. Rend. Acad. Sci. Paris, T. 17, pp. 662-675. 
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Verworn, M. 
91. Gleichgewicht und Otolithenorgan. Arch. f. ges. Physiol., Bd. 50, 
pp. 423-472. 


PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 2 


Or 
— 


EXPLANATION OF THE PLATES. 


All Figures were outlined with an Abbé camera lucida. Tube length was 
usually 160 mm., with projection distance to the table, 410 mm. The magnifi- 
cations are given with the descriptions of the several figures. Drawings were 
made from sections, unless the contrary is stated. The orientation of the figures 


is given for each plate. 


ABBREVIATIONS. 
el.gl. . . . Gland cell. nl. tu. 
cl.gn. . . . Ganglion cell. n. opt. 
cl.ma.. . . Matrix cell. n. ot. 
cont. cre’oes. | Cireumcesophageal con- n’pil. at.1 . 

nective. n’pil.at.2 . 
crs. sns. . . Sensory crista. n’pil. opt. . 
cla ee Cuticula: n. teq. 
ca’. . . . New cuticula. Ui. 
dite. uct: olcy. 
for’. . . . Fibrillations. ot lth. 
for.ass. . . Association nerve fibre. pinn. 
for.c. . . . Central nerve fibre. pre. pr’pl. 
for.n.. . . Nerve fibre. rm. l. 
for. pi’ph. . . Peripheral nerve fibre. 
ie o o 6 « llerllinyey ro. 
Gib eee (Globulus: Schau. 
gn. olf.. . . Olfactory ganglion. set. fil. . 
Wdrm. . . . Hypodermis. set. 1. 
lab.a. . . . Anterior lip of orifice set. m. 

to otocyst. set.olf. . 
iab.p. . . . Posterior lip of same. set. ot. 
lu. . . . . Lumen of otocyst. set. p. 
mal.. . . . Hammer. set.ta. . 
mb.sph. . . Spherical membrane. set. tac. 
n.at.1. . . Antennular nerve. tb. set. . 
nat.2@ . . . Nerve of 2d antenna. iso 6 
n’bl.. . . . Neuroblasts. tu. myl. 


nlem . . . Neurilemma. 


Sheath nucleus. 

Optic nerve. 

Otic nerve, 

Neuropil of antennule. 

Neuropil of antenna. 

Optic neuropil. 

Tegumentary nerve. 

Orifice. 

Otocyst. 

Otoliths. 

Pinnules of hairs. 

Protoplasmic process. 

Lateral branch of an- 
tennular nerve. 

Rostrum. 

Group hairs. 

Thread hairs. 

Laterai hairs. 

Median hairs. 

Olfactory hairs. 

Otic hairs. 

Posterior hairs. 

Hook hairs. 

Tactile hairs. 

Hair tube. 

Tectum of otocyst. 

Myelin sheath. 


PRENTIss. — Otocyst Crustacea, 


PLATE 1. 


All Figures are of Palemonetes. In Figure 1 anterior is up on the plate ; 
in Figures 2, 8, and 4 the dorsal side is up, and the anterior end in Figure 4 is at 


the left. 


Lines numbered 2, 3, 4, 5 in Figure 1 indicate the planes of the sections 


shown in Figures 2, 3, 4, and 5 respectively. 


Fig. 


IE 


bo 


Dorsal view of the basal segment of both antennules, showing otocysts 
and the arrangement of the hairs in the sac. X 30. 

Somewhat oblique transverse section, extending from dorsal anterior to 
ventral posterior, of both antennules and the rostrum, through the 
posterior ends of the otocysts (compare line 2, Fig. 1). X 64. 

Transverse section of right antennule through the orifice of the sac, show- 
ing tectum and otoliths (compare line 3, Fig. 1). 64. 

Parasagittal section through right antennule and brain, showing the 
course of the otic nerve, with a single nerve element drawn diagram- 
matically (see line 4, Fig. 1). X 64. 


ar a a at = emer mee reer Try AAT St TOMA AT + = 
tATI Ss— Teo So ECAPOD UR > G / . = l 


22 aces 2 Q9b np OF 
pAZ SES? 9 a aged 2 Bea 
ee ae 


° 


: Eee ’ 


fo n A ft retaining) 
"00.0.9 eae 
be Ss ais Pg 
= J“ ia 
s i 


OL Ura Ge Ly 

is HL ie nha eon 

a a Reais Chr 

. Ce) NE Tan Sicee 
“ ba Cae tee j 


~~ 


ae 


PRENTIss. — Otocyst Crustacea. 


PLATE 2. 


All Figures are of Palemonetes. The dorsal side is up in Figure 5, and the an- 
terior end at the right. 


Fig. 5. Parasagittal section through the lateral side of the right otocyst (see line 
Seip) ae OA: 

Fig. 6. Transverse section through the posterior end of the sensory cushion, 
showing two lateral hairs, the base of a median one and a group of 
ganglion cells. X 168 

Fig. 7. Otocyst hair and matrix cells. 600. 

Fig. 7a. Another otocyst hair and matrix cells. X 600. 

Fig. 8. Sensory hair of the otocyst and the ending of its peripheral nerve fibre. 
x 600. 

Fig. 9. Fundament of developing sensory hair from an abdominal exopod, 
showing matrix cells about the nerve fibre. Methylen-blue prepara- 
tion. X 600. 


PRENTISS—OTOCYST GRUSTACEA. PLATE 2. 


— 


\ — 


CWP del. B. Meisel, lith. Boston 


j ry 0.6 


sah 1 ae hapa a ann ity eA: el hae 
io, Le. hi ic au re Oy I 
Sa hy le tia ie Pa a es rp in : ee an 
4 - on) Hit Nal PONE i Pe Se 
i a r i Hi aa sip sata 

i $e Op. eer! AMA 1m rite toh fp wi ame 

7 ied ale hh a Sd; Ta ae Hy i wer: Ah in 

SA) iy ea ap hy iin wh hae iy As, 


{ 


= 


i 


PRENTIss — Otocyst Crustacea. 


PLATE 3. 


All Figures are from methylen-blue preparations of Palcemonetes. Anterior is 
up on plate in Figure 12. 


Fig. 10. Part of abdominal exopod showing tubes of developing tactile hairs and 
their innervation. X 125. 

Fig. 11. Peripheral nerve endings in the tactile hairs of the second maxilliped. 
x 96. 

Fig. 12. Dorsal view of antennules and brain, showing sensory neurons and cen- 
tral endings of the otocyst nerve fibres. The peripheral endings in 
the left otocyst are diagrammatic. x 30. 


PRENTISS—OTOCYST CRUSTACEA. AMIE Ne 3 


pil ab 2. oa - 


= a 


/ —— (\  npilate. 
= | ea 


\ fino Se 
——— i eet 
\ ~\-ont.cre.oes. = \ 


CWP del B Meisel, lith. Saston 


PRENTISS. — Otocyst Crustacea. 


PLATE 4. 


Figures 13-18 are of Palemonetes. Figures 19-22 are of lobster larve. In Figures 
19-21 dorsal side is up and the lateral side is at the right; in Figure 22 anterior 
is at the right, dorsal side up. 


Fig. 13. 


Fig. 


14. 


alias 
1G}. 


mite 
als: 
ig. 19. 
20. 
ai 


22s 


Portion of inner flagellum of first antenna, showing olfactory hairs and 
their peripheral ganglionic masses. Methylen blue. X 125. 

Gustatory hairs and nerve elements from the basipod of second maxilia. 
Methylen blue. X 95. 

Fibrillations in peripheral otic nerve fibre. Methylen blue. X 1800. 

Ganglion cell of otocyst and peripheral nerve process surrounded by 
myelin sheath. > 600. 

Ganglion cell of otocyst, and sheath nucleus. X 1500. 

Ganglion cell of otocyst. Methylen blue.  X 770. 

Transverse section through right antennule of first lobster larva. X 168. 

Transverse section through right antennule of second lobster larva; 
beginning of invagination. X 168. 

Transverse section through right antennule of third lobster larva. 
x 168. 

Parasagittal section through antennule of second lobster larva. X 168. 


— 


<A 
"foo 


ergge 2 


Peal 
7. io 
if 3 
pat She 3 
ps : 
fe ‘| 
ve ’ 
ay i 
“ 
: 
, { 
> 
>. 
. 
Sy 
. 
“a 
s 
. 
* 
e/ 
L ) 
Me) 
s 
2 5 
o r) 


ae li rah 


vr) Oy bry ae ea i oan nen ye 
ie iy bai lke ty) ek : in Mn ite He mY) aT) ra | v An) da Act rie i ise . aye 
; : | oe ie Pe aah i “he 
4), Dh ; y van i Oe ey Tepae Mra Aas ae ‘ val ate) A 

- _ 4 z Higy we Ba Anan ita Gap i Mis? Li ms) 
: a al eu Pras) rake: aU Ral nica ie a a ie 
vt ily a | iF 


a : - a ie ve 7 Pi eh; i. : 
ia ‘ i 


i] : . \ 
| / : a 
‘9 . 
ae us uf na 
- ny ‘ 
’ ; 
Fi ! 
As ~ } | 
t a i 
Mi } 
} I Dy lt 
4 : f Pt 
’ t 
i 
rs | 
i 
Oa eer — =~ 
as th 
5 j ; ‘VA i) iy 
“) an f 
} ee cas w 
ee iets whi 
; i 
‘ Le 
f } » eas 
: ¥ 
- P 
f mi } ' 
I Wa ¥} 
a; UU Uty 
are 2: 4 


PRENTISS. — Otocyst Crustacea. 


PLATE 5. 


All Figures are of lobster larve. In Figures 23 and 25 dorsal is up, and anterior 
at the right ; in Figure 24 dorsal is up and lateral is at the right; anterior is at 
the right in Figure 26. 


Fig. 23. 
Fig. 24. 


Fig. 25. 
Fig. 26. 


Parasagittal section through the antennule of the third larva. X 168. 

Transverse section through the posterior part of the right otocyst in 
fourth larva. X 168. 

Parasagittal section of the same. X 125. 

Diagrammatic dorsal view of floor of right sac dissected out to show 
arrangement of the hairs and their innervation. Methylen blue. 
x 168. 

Developing hairs of the otocyst in the third larval stage. X 600. 


ge e** 
fe * 6 
+ Ae “s 
N fe 
A’ 9s 
fie x 
Ke / 
i y 
pad 
i} ; e / 
\ aad 
} / | | 
j je | 
4 12 6/ 
\ 
Py 
“cS ie ‘ 
, i“ | | 
: fs 
 ) 
c’/ 
A " 
fe « 
Ww 
fr 9 
ies a 
A 
j { AS Ne 
i) a aS | 
c 
Be 1 Te ass be 
Ye a % 3 
° Wess ssesstes yew 
\ 
e\ 
~ 
ba | 
iN 


ote? 


SEES Soycoue 


PRENTIss. —- Otocyst Crustacea. 


PLATE 6. 


Crangon ; in Figure 28 dorsal is up; in Figure 29 anterior is up. 


Fig. 28. Transverse section of both antennules through the sensory cushions of 
the otocysts. x 965. 

Fig. 29. Reconstruction from ten frontal sections through the base of both anten- 
nules and the brain. A semi-diagrammatic nerve element is shown 
at the left in black. X 985. 


2 eh 
pense OsgngpLees oan’ 
Spr SN iege abe 7 

yt) am y 


ff, aettsd 
ARENT eae 


PRENTISS. — Otocyst Crustacea. 


PGA El. 


Figures 30 and 31 are of Crangon. All others are of Cambarus. In Figure 30 
dorsal is up and lateral is at the left ; in Figure 36 dorsal is up and lateral is at the 
right. 


Fig. 
Fig. 
Fig. 
Fig. 


Fig. 


30. 
él. 
32. 


33. 


Parasagittal section of antennule and brain. x 95. 

Otocyst hair. X 600. 

Olfactory hairs from basipod of second maxilla, showing innervation. 
Methylen blue. X 95. 

Posterior row of otocyst hairs and their nerve elements. Methylen 
blue. X 95. 

Tactile hair from scaphognathite of second maxilla, showing innervation. 
Methylen blue. X 95. 

Transverse section through shaft of otocyst hair. X 770. 

Diagrammatic transverse section of the right antennule through the pos- 
terior part of the otocyst. X 16. 


PRENTISS—OTOCYST CRUSTAGE A. PRATE 7 


seh tac. “0 


; : a ane 

, a 4 / } I y | ) i, ve : ; q F i a y F 
| : | | : : | 

Ms : S 

Seay : iS ; eee ? Zod” } LY 
re: 1 Foo = 90 00 8 e 
‘AE Se x c : 00 : r # ° 
= ~ << P) fae Y 
qo 
CWP. del B. Meisel, jith. Boston 


é 7 
: yarn 
' 7 Yanai i 
om ar arr an 


hi a 


PRENTIss. — Otocyst Crustacea. 


PLATE &. 


All Figures are of Cambarus. Dorsal side is up in Figures 37 and 38 ; in Figure 
38 anterior is at the left; anterior is up in Figure 40. 


Fig. 37. 


Fig. 38. 
Fig. 39. 
Fig. 40. 


Transverse section through the orifice of both otocysts ; left antennule is 
diagrammatic. X 26. 

Parasagittal section through right antennule and brain. X 26. 

Tegumentary gland from the sensory cushion of the otocyst. X 600. 

Dorsal view of the sensory cushion of the left otocyst dissected out, 
showing the arrangement and innervation of the hairs. Metbylen 
blue. X 62. 


Sa 
tee, 


aA tee ran area ttt 


\\ set.L. 


Ahi me ce 

i { mh i O¥ig ike i 

mL Yin ae nee o va 
A) Say nal if Ni 


Apa 


ft? x Pai ir 
TPG MaELLA ea 
} FA se H 5 de 

hy ‘il Pate) nur My, Weim 
4 : ae mye i us aint es 
th UL Ke au: ‘ Mi Be 

ne ae tbat 7 Ni va le 


ata ‘ hie Cah 


ve 
- ul 
Ln ' iy | rae 
i i 3 ’ ra 
; ih 
_ j i ayy) 
. en ane 
1 ¥ ’ Cave 
‘ i 
j } i a? 
; } Ritey, ; 
ut 7 i] 
7) j ih ap ar 
t uke 
i ' ; ; . 
i] 
7 rh 
Pits i U 
i) ni i 
i 
as a: 
im u 
ip . Uj 
Pana) 


de F \ | of, 
: : ur ore) ty, " 
hy ea ey ' / yey rf it f} 
cae Pe ee 
o haWe 1 
es) if 4 i ware. 
ope \ ; ' ik 
_ a ray ae sy L : 
ier ih 7 7 a 
i a] + Ug 
{ : yy ae 4 
a ar yi 4 Oa + 
/ 


a i 
Waser We 
i : i= yen 
ae - 
{ it? aa 
7 Verh 7 : ~— i 


PRENTIsS. — Otocyst Crustacea. 


PLATE 9. 


Figure 41 is of Cambarus; all others are of Carcinus. In Figures 41 and 46 
anterior is up; in Figures 42-45 dorsal is up and anterior at the left; in Figures 
47 and 48 dorsal is up and lateral is at the right. 


Fig. 41. Ventral view of brain, showing central endings of otic and antennular 
nerves. Methylen blue. X 30. 

Figs. 42-45. Outlines of four parasagittal sections through the left otocyst of 
Carcinas, cut along the lines of section marked with corresponding 
numbers in Figure 46. Figure 45 is most median, Figure 42 most 
lateral in position. XX 16. 

Fig. 46. Dorsal view of both antennules. Numbered lines (42-48) indicate planes 
of section of corresponding Figures. X 8. 

Fig. 47. Transverse section through the orifice of right otocyst (see Fig. 46, line 
47). X 16. 

Fig. 48. Transverse section through anterior end of the otocyst (see Fig. 46, line 
48). X15. 


‘ 
7 
PRENTISS—OTOCYST DECAPOD CRUSTACEA. PLATE 9 


GWE del. 


fon 4 his - . 
& ety ky ; 


Fig. 
Fig. 


Fig. 
Fig. 


Fig. 
Fig. 
Fig. 


PRENTIss. — Otocyst Crustacea. 


49. 
50. 


61. 
52. 


53. 
54. 
56. 


PLATE 10. 


- All Figures are of Carcinus ; anterior is up in Figure 55. 


Group hair. X 600. 

Transverse section through the sensory cushion of the hook hairs. 
< 168. 

Hook hair. X 600. 

Portion of outer flagellum of antennule, showing the bases of olfactory 
hairs and their innervation.  X 95. 

Thread hairs and their nerve elements. Methylen blue.  X 95. 

Tip of thread hair. X 1300. 

Nearly frontal section, inclining dorsal and forward, through both anten- 
nules and brain. X 25. 


PRENTISS—OTOCYST GRUSTAGEA. PLATE 10. 


CWP del B Meisel, lith. Beston 


i 7 rts 
orn) ve re 


ne i 


| bee : : 


re 
ae 7 7 = see 
* - path 


7 
1 


; ra 
At - 
7 
1 
DF, ; - 
ae ; 
8) ee 
a 
il _ 
L 
— 
iif 
7 
= 
ion 
7 
a0 > 
= - a . 


The following Publications of the Museum of Comparative Zodlogy 
are in preparation : — 


Reports on the Results of Dredging Operations in 1877, 1878, 1879, and 1880, in charge of ALEX- 
ANDER AGASsiz, by the U. S. Coast Survey Steamer “* Blake,” as follows: — 


E. EHLERS. ‘The Annelids of the ‘‘ Blake.” 

CG. HARTLAUB. The Comatuls of the ‘‘ Blake,” with 15 Plates. 

H. LUDWIG. The Genus Pentacrinus. 

A. MILNE EDWARDS and E. L. BOUVIER. The Crustacea of the “ Blake,” 
A. E. VERRILL, ‘The Alcyonaria of the “ Blake.” 


Reports on the Scientific Results of the Expedition to the Tropical Pacific, in charge of 
ALEXANDER AGASSIZ, ou the U. S. Fish Commission Steanier ‘‘ Albatross,’ from August, 
1899, to March, 1900, Commander Jefferson F. Moser, U. S. N , Commanding. 


Illustrations of North American MARINE INVERTEBRATES, from Drawings by BuRK- 
HARD? SONREL, and A, AGASsiIz, prepared under the direction of L. AGASSIZ. 


LOUIS CABOT, Immature State of the Odonata, Part 1V. 
E. L. MARK. Studies on Lepidosteus, continued. 
tf On Arachnactis. 
R. T. HILL. On the Geology of the Windward Islands. 
W. McM WOODWORTH. On the Bololo or Palolo of Fiji and Samoa. 
A. AGASSIZ and A. G. MAYER. The Acalephs of the East Coast of the United States. 
AGASSIZ and WHITMAN. Pelagic Fishes. Part II., with 14 Plates. 
J. C. BRANNER. ‘The Coral Reefs of Brazil. 


Reports on the Results of the Expedition of 1891 of the U. S. Fish Commission Steamer 
“ Albatross,” Lieutenant Commander Z. lL. TANNER, U.S. N., Commanding, in charge of 
ALEXANDER AG&ssiz, as follows: — 


A. AGASSIZ. ‘The Pelagic Fauna. H. LUDWIG. The Starfishes. 
a The Kehini. J.P. McMURRICH. The Actinarians. 
se The Panamic Deep-Sea Fauna. KE. L. MARK. Branchiocerianthus, 
K. BRANDT. The Sagitte. JOHN MURRAY. ‘The Bottom Specimens. 
Me The Thalassicolss. P. SCHIEMENZ. ‘The Pteropods and Hete- 
CG. CHUN. ‘The Siphonophores. ropods. 


ue The Eyes of Deep-Sea Crustacea. THRO. STUDER. The Alcyonarians. 


W. H. DALL. ‘The Mollusks. +: 5 
_P. A. TRAUTSTEDT. The Salpide and 
H. J. HANSEN. ‘The Cirripeds. i BOP Saas: ctearti sop 


W. A. HERDMAN. ‘The Ascidians. Doliolidee. 

S. J. HICKSON. ‘The Antipathids. E. P. VAN DUZEE, The Halobatids. 

W. E. HOYLE, The Cephalopods. H. B. WARD. ‘The Sipuncullds. 

G. VON KOCH. The Deep-Sea Corals. H. V. WILSON. The Sponges. 

C. A. KOFOID. Solenogaster. W. MoM. WOODWORTH. ‘The Nemerteans. 
R. VON LENDENFELD. ‘The Phospho- “ The Annelids, 


rescent Organs of Fishes. 


Rg 


PUBLICATIONS 


OF THE 


MUSEUM OF COMPARATIVE 


. * gases 
ZOOLOGY — 


AT HARVARD COLLEGE. 


There have been published of the BuLLerins Vols. I. to XXXV.; 7. 08 
of the Memoirs, Vols. I. to XXIV. ae 

Vols. XXXVI., XXXVII.,.and XXXVIII._ of the Boies : 
and Vols. XXV., XXVL. and XXVII. of the Bhomau, are now 
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The Buuterin and Memorrs are dewtind to the eee of 
original work by the Professors and Assistants of the Musenm, of 
investigations carried on by students and others in the different. 
Laboritories of Natural History, and of work by specialists based 
upon the Museum Collections and Explorations. : 


The following publications are in preparation : — 


Reports on the Results of Dredging Operations from 1877 to 1880, in-charge of 
Alexander Agassiz, by the U. S. Coast Survey Steamer “ Blake,” Lieut. 
Commander C. D. Sigsbee, U. S. N., and Commander J. R. Bartlett, U.S. N., 
Commanding. 

Reports on the Results of the Expedition of 1891 of ns U.S. Fish Commission 
Steamer “ Albatross,” Lieut. Commander Z. I. Tanner, U. S. N., Com- wae 
manding, in charge of Alexander Agassiz. 

Reports on the Scientific Results of the Expedition to the Tropical Pacific, i in 
charge of Alexander Agassiz, on the U.S. Fish Commission Steamer — 
“ Albatross,” from August, 1899, to March, 1900, Commander Jefferson Bas 
Moser, U. S. N., Commanding. ; 

Contributions from the Zodlogical Laboratory, Professor KE. L.. Mark, Director. 

Contributions from the Geological Laboratory, in charge of Professor N. S. — 
Shaler. 


These publications are issued in numbers at irregular inter- 
vals; one volume of the Bulletin (8vo) and half a volume of the 
Memoirs (4to) usually appear annually. Each number of the Bul- 
letin and of the Memoirs is also sold separately. A price list 
of the publications of the Museum will be sent on application 
to the Librarian of the Museum of Comparative Zodlogy, Cam- 
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ON A 


| ISLANDS. Thy: 5 Gi due ai { day, 
oe ONIEN DE Thee) 


By Ourram Banes. 


_. CAMBRIDGE, MASS., U.S. A.: 
PRINTED FOR THE MUSEUM. 
Jury, 1901. 


— 


Bulletin of the Museum of Comparative Zodlogy 
AT HARVARD COLLEGE, 
Vout. XXXVI. No. 8. 


ON A COLLECTION OF BIRDS FROM THE LIU KIU 
ISLANDS. 


By Outram Banas. 


CAMBRIDGE, MASS., U.S. A.: 
PRINTED FOR THE MUSEUM. 
Juxy, 1901. 


~f 


No. 8.— On a Collection of Birds from the Liu Kiu Islands. 
By Outram BANGs. 


THE Museum has recently acquired from Mr. Alan Owston of Yoko- 
hama an interesting collection of birds from the Yayeyama, or southern 
group of the Liu Kiu Islands. Though consisting of but one hundred 
and seven specimens, comprising fifty-six species, it contains six forms 
apparently hitherto undescribed. The collection was made by Mr. 
Ishida Zensaku and assistants from February to July, 1899, mostly in 
the Island of Ishigaki; some of the species were taken in the islands of 
Taketomi, Kobama, Hamarlijima, Kuroshima, Hatojima, and Iruduroto. 
The systematic sequence adopted is that of Stejneger in his Catalogue of 
Birds hitherto recorded from the Liu Kiu Islands.’ I am indebted to 
the Museum authorities for placing the collection at my disposal for 
study, and am under special obligation to Dr. Leonhard Stejneger of the 
United States National Museum. Dr. Stejneger has made extensive 
studies of the fauna of the Liu Kiu Islands, and his aid and advice in 
comparing the specimens of the present collection with those in the 
National Museum have been of great value. 1am also indebted to Mr. 
E. W. Nelson of the Biological Survey for comparing the noddy and 
sooty terns with those in the Department of Agriculture collection. 
In the following descriptions all measurements are in millimetres; the 
wing is measured in its natural curve, and not flattened down on the 
rule; the tail is measured by thrusting one point of the dividers to 
the base of the tail feathers and measuring thence to the_tip of the 
longest rectrix. All colors, when definitely expressed, are according to 
Ridgway.” 


Sterna melanauchen Temm. 


Two specimens, adult ¢ and adult 9, from a small island near Taketomi, 
were taken June 20. [Eggs were collected from June 25 to July 5; a single 
egg laid on the ground. ]8 


1 Proce. U. S. Nat. Mus., 1887, Vol. X. pp. 414-415. 

2 Ridgway, R. A Nomenclature of Colors for Naturalists, etc. Boston, 1886. 

3 A list of the Zensaku collection, containing many notes on the distribution, 
nesting habits, etc., of the species taken, was published by Mr. Alan Owston (Yo- 
kohama, 1899). In this paper extracts from Owston’s list are in brackets. 

VOL. XXXVI. — NO. 8 


bo 
OU 
ler) 


BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


Sterna dougalli gracilis (Goutp). 


Two specimens, an adult ¢ and an adult 9, taken June 7 on a small island 
near Ishigaki. [Eggs were collected from June 19 to July 5.] These speci- 
mens are extreme of the slender-billed small form to which Gould’s name 
gracilis applies. Specimens from western Europe and Africa agree closely in 
measurements with those from eastern North America and the West Indies. 
The red bill claimed as a character of gracilis may be due to age, many young 
specimens from America having red bills, while in the adult birds it is black. 
The differences between the two races of the Roseate Tern in size and in measure- 
ments of the bill are well marked. 

The Liu Kiu Islands specimens agree in measurements with the. Australian 
form, upon which Gould based his S. gracilis, and there can be no doubt of 
their identity. 

The measurements of the two specimens are as follows : — 


No. Sex. Wing. Tail. Tarsus. Exposed Culmen. 
37,304 os 221 110 20.2 36.6 
387,305 g 216 109 19.4 36. 


Sterna fuliginosa crissalis (Barrp). 


Two specimens from a small island near Iriomote, adult g and adult Q, 
taken June 10. [Eggs, one in a clutch, laid on the rock, were taken June 1. ] 


Sterna bergii boreotis,? subsp. nov. 


Typr. — Mus. Comp. Zodl., No. 37,801. 


_ Asingle adult g in full breeding plumage from Ishigaki, June 15, 1899. 
[Said to breed on Ishigaki.] 

Subspecifie Characters. — As small as the pale gray Sterna bergii poliocerca of 
Tasmania and South Australia ; differing from it in having the wings, tail, and 
mantle very dark smoke gray, almost mouse gray. 

Color. — Type, adult ¢ in full plumage. Forehead, cheeks, lores, ear-coverts, 
neck all round, and whole under parts, including lining of wing and bend of 
wing, pure white ; crown and long occipital crest glossy black ; mantle, wings, 
rump, upper tail coverts, and upper surface of middle rectrices dark smoke 
gray, darkest on wings and middle of back, where the color is almost mouse 
gray ; primary quills white; Ist primary with outer web, a band along quill 
on inner web and tip blackish, with a silvery suffusion which is most marked 
toward centre of feather; broad outer margin of inner web, below the black tip 


1 The tails are measured to the end of the second rectrix, the streamer varying 
too much in length individually to be taken into account. 
2 Boreotis, northern. 


BANGS: BIRDS FROM THE LIU KIU ISLANDS. 25-1 


white ; 2nd primary similar but black tip deeper in color and extending a short 
distance down outer margin of inner web, thus enclosing the white of inner 
web for a short distance; 3rd, 4th, and 5th primaries like 2nd, but black tip 
gradually growing deeper in color; outer rectrices above pale smoke gray at 
tips and along shafts, pale grayish white toward base; 2nd and 3rd rectrices 
darker on the outer webs and at tip and whitish toward base of inner webs ; 
bill, in dried specimen, dull yellow clouded with olive toward base; feet and 
tarsi blackish. 

Measurements1— Adult @, type, wing 344; tail 178; tarsus 28; 
culmen 62. 

Remarks. — Sterna bergii was first recorded from this region (breeding on 
small islands off the north coast of Formosa) by Swinhoe (Ibis, Vol. II. p. 68, 
1860); since then two specimens have been noted by Stejneger, both from the 
Yayeyama Islands, the first in Proc. U. S. Nat. Mus., 1887, Vol. X. p. 392; 
the second in Vol. XIV. p. 490, 1891. But the question Stejneger raised in 1887, 
“ Will anybody kindly inform me what name properly belongs to the smaller 
dark birds from the China seas? ” has hitherto remained unanswered. My type 
of Sterna bergii boreotis agrees with the descriptions of Stejneger’s specimens, 
and I propose for the smal]l dark northern form of Bergius’s tern the trinomial 
given above. When Saunders wrote his account of Bergius’s tern, he hada large 
series of specimens at his command. He devotes but a few lines to the 
exceedingly interesting geographical variations of this wide-spread species, and 
after pointing out, in rather a vague way, how well marked the various races 
are, ends by including them all under one name. 

The principal races of Sterna bergiit may be indicated as follows : — 

1. Sterna bergit bergit Licht., South Africa, large, gray of upper parts pale. 

2. S. bergit velox (Cretzschm), Red and Arabian Seas and Bay of Bengal, 
large, gray of upper parts very dark. 

3. S. bergit pelecanoides (King), northern parts of Australia, intermediate 
between the last two in size and coloration. 

4. 8S. bergit poliocerea? (Gould), Tasmania and South Australia, small, gray of 
upper parts pale. 

5. 8S. bergi boreotis, subsp. nov., Liu Kiu Islands and Northern China 
Sea, small, gray of upper parts very dark. 

Still another race that may prove distinct is the Polynesian 8. rectirostris 
Peale, described from the Fiji Islands. 


1 Three specimens of S. bergii poliocerca in the Mus. Comp. Zool. afford the 
following measurements : — 


No. Sex. Locality. Wing. Tail. Tarsus. Culmen. 
8,781 g Australia. 334 158 81 59.5 
12,018 g (2) Melbourne, Aust. 332 173 27 56. 
8,782 3 (2) Australia. 340 146 30 59. 


For further measurements, see Stejneger, Proc. U.S. Nat. Mus., 1887, Vol. X. 
pp. 393-394. 


258 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


Anous pullus,! sp. nov. 


Type. — Mus. Comp. Zodl., No. 37,298. 


Two specimens, an adult ¢ and an adult 9, from a small rocky island near 
Iriomote, June 10. [Eggs, one in a clutch, laid on the bare rock, were taken 
July 1.] 

Characters. — A large very dark brown .noddy with a gray crown, nearest to 
A. rousseaut Hartl. of Madagascar and adjacent islands, from which it differs 
by being much darker in color and slightly smaller in size. 

Color. — Adults, in unworn, full breeding plumage. Narrow superciliary 
streak, ending above eye, lower eyelid, and a spot on upper eyelid whitish ; 
forehead pearl gray, this color extending over crown and gradually darkening 
to slate gray on occiput, and thence merging on hind neck into the brown 
of upper parts; lores and region above the eye below the whitish streak black; 
upper parts rich dark chocolate brown, with a slight grayish cast; primaries 
and rectrices dark blackish brown; chin and sides of head blackish slate ; rest 
of under parts deep chocolate brown ; lining of wing brownish slate ; bill, in 
dried specimens, black ; feet and toes reddish brown. 


Measurements : — 
No. Sex. Wing. Tail. Tarsus. Culmen. 
37,297 3 Topotype. 273 164.5 25. 39. 
37,298 9 Type. 271 159.5 24.5 38. 


Remarks. — A comparison of the two specimens upon which I base this new 
noddy with the material in the National Museum and the Museum of Com- 
parative Zodlogy shows them to be much nearer to A. rousseaut than to any 
of the other forms. The comparison was made with skins of A. rousseaut 
from the Seychelles and Mauritius. The Liu Kiu birds are much darker in 
color throughout, especially so about chin, sides of neck, and breast, and_ they 
are also smaller, the wing of the Mauritius specimen being 285 mm. long, and I 
have no hesitation in proposing a name for the Liu Kiu noddy. 

Compared with other noddies, the differences are still greater ; thus the Liu 
Kiu form is much darker than A. ridgwayi Anthony from Socorro and Tres 
Marias, especially about sides of head and throat, and the crown is darker and 
grayer. 

From A. galapagensis Sharpe the new species differs in not having so black 
a body or such a dark gray crown. 

From the noddy of eastern America —true A. stolidus —the Liu Kiu bird 
is very distinct, and can at once be told by its larger size and gray crown and 
forehead, the forehead and most of the crown in A. stolidus being white or 
yellowish white. 

A. pullus differs much from the small slender-billed species, A. leucocapillus, 
A. hawaiiensis, and A. tenuirostris, in being larger and having a stouter bill. 


1 Pullus, dark-colored, dusky. 


BANGS: BIRDS FROM THE LIU KIU ISLANDS. 259 


Puffinus leucomelas Temm. 


Two specimens from a small island near Iriomote, taken June 7. [One 
egg was taken July 1, from a hole in the rock about six feet deep. ] 


Bulweria bulweri (Jarp. & SELB.). 


One adult 9 from Hanarejima, June 25. [Two eggs supposed to belong to 
this species were taken on the same island, June 20. ] 


Arenaria interpres (Lrny.). 


One adult ¢ in full plumage, Ishigaki, May 10. 


Charadrius dominicus fulvus (Gmet.). 


Two females from Ishigaki, March 1 and June 1. 


Aegialitis alexandrina (Liyy.). 


One specimen, March 13, Ishigaki. [Eggs were collected, April 29 to 
June 20.] 


Ochthodromus mongolus (PALL). 


One 9 from Ishigaki, June 1. 


Actitis hypoleucos (Liyx.). 


One 9 from Ishigaki, March 12. 


Heteractitis brevipes (VI£ILL.). 


One 9 in winter plumage, Ishigaki, March 12. 


Gallinago gallinago (Liny.). 
One @ from Ishigaki, March 25. 


Limnobenus pheopygus (Srerusn.). 


Three specimens from Ishigaki, adult ¢ taken May 1, adult 9 June 20, and 
achick June 19. The chick is covered with black down, which on the back is 
shining blue black, the bill and a patch of bare skin below the eye are yellow. 


260 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


The wing in the adult @ is 105.4, in the adult 9 104. Neither of these has 
white spots on the outer web of Ist primary, such as Stejneger describes. 


[Nests containing six eggs each were found among reeds from April 10 to 
July 4.] 


Rallina sepiaria (SreEsn.). 


Two adults from Ishigaki, @ taken March 20 (wing 146), 9 taken April 
2 (wing 150). 


Gallinula chloropus orientalis /Horsr.). 


Two adults, ¢ and 9, from Ishigaki, taken March 21. 


Fuligula fuligula (Lrxy.). 
Two adults from Ishigaki, 9 taken May 20, @ June 13. The male lacks the 
white spots on the chin. 
Anas zonorhyncha Swinu. 


Two adults from Ishigaki, g May 10, 9 Junel. [Many nests were found 
placed on the ground among grass, and eggs, seven in a clutch, taken from 
April 19 to June 25. ] 

Nettion crecca (Linx). 


One female from Ishigaki, March 7. 


Dendrocygna! javanica (Horsr.). 


Two adults from Ishigaki, g taken May 25, 9 June 1. [Nests were found 
on the ground among tall grass, and eggs, six in a clutch, taken from May 31 
to June’21.] 


Sula sula (Lryy.). 


Two specimens, adult ¢ from Iriomote, June 20, adult 9 from Ishigaki, 
June 15. [Eggs were found two in a clutch, on outlying rocks, May 12 to 


June 13.] 
Gorsachius melanolophus (Rarrtes). 
Two adults from Ishigaki, g March 23, 9? June 7. 


1 This name is by many ornithologists improperly spelled, “ Dendrocycna.” 
Swainson’s original spelling was “ Dendrocygna.” 


BANGS: BIRDS FROM THE LIU KIU ISLANDS. 261 


Demiegretta ringeri Srrsn. 


One fine adult female, taken in Ishigaki, March 25. This skin agrees with 
Stejneger’s description, and the northern reef heron is a valid form, differing, 
as pointed out by Stejneger, from the southern reef heron in its gray head and 
occipital crest. It is, however, not recognized by Sharpe in the Catalogue of 
Birds in the British Museum. 


Nannocnus eurythmus (Swiyz.). 


Two adults from Ishigaki, ¢ taken March 25, 9 June 10. [Nests built in 
reeds about two feet from the ground, containing six eggs each, were found 
from May 19 to July 3.] 


Pyrrherodias manillensis (Mryrey). 


Six specimens, all from Ishigaki, adult ¢ June 20, adult 9 May 20, and four 
nestlings June 1. [Eggs were taken from April 22 to May 19. The nests 
were placed on oak and other trees, at from 20 to 30 feet from the ground, and 
usually contained four eggs each. ] 

This heron was first recorded from the Yayeyama Islands by Stejneger in 
1891, who doubtfully referred! it to Ardea purpurea Linn., but pointed out 
differences from that species. At that time the relationship of the two mem- 
bers of this genus, purpurea and manillensis, was not understood. The Ishigaki 
specimens appear to be typical P. manillensis, though I have had but few 
skins for comparison. 


Turnix taigoor (Sykes). 


Four specimens from Ishigaki, adult ¢ taken April 25 (wing 77), adult 9 
April 25 (wing 84), and two chicks taken April 12. [Eggs, four in a clutch, 
were taken from March 17 to July 3.]_ This is the Turnizx blakistoni (Swinh.) 
of Stejneger (Proc. U. S. Nat. Mus., 1886, Vol. IX, p. 635). Dr. Stejneger 
now agrees with me in the identity of these two forms. 


Sphenocercus medioximus,? sp. nov. 


Type. — Mus. Comp. Zodl., No. 37,349. 


Two adults from Ishigaki, g taken March 9, 9 March 7. Specimens were 
secured on this island from February 2 to June 5. [Nests containing two eggs 
each were found on trees at from six to ten feet from the ground, between 
April 25 and June 2.] 


1 Proc. U. S. Nat. Mus., 1891, Vol. XIV. p. 493. 
2 Medioximus, middlemost, holding a middle place. 


262 — BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


Characters. — Nearest in color to S. permagnus (Stejn.) from the middle 
group of the Liu Kiu Islands, but much smaller, being little larger than 
S. formose (Swinh.) of Formosa. 

Color. — Type, adult ¢. Forehead yellowish oil green, slightly shaded with 
chestnut toward crown ; rest of upper parts dark oil green, the feathers of the 
cervix, sides of head and neck and upper back, pale gray below the green tips, 
this color showing through a little, giving a hoary cast to these parts ; rump 
and upper tail coverts a little brighter; primaries slaty black with a percep- 
tible greenish tinge toward ends, the three outer ones narrowly edged with yel- 
lowish; secondaries, alula, and middle coverts slaty black somewhat washed 
with green ; middle coverts and secondaries bordered externally with yellow; 
rest of wing and scapulars oil green with a slight wash of chestnut on shoul- 
der; under parts yellowish oil green; middle of belly and striping on flanks 
yellowish white ; under tail coverts (reaching to end of tail) dark oil green 
broadly edged with straw yellow ; rectrices above olive green, below slaty 
black with grayish tips; under surface of wing slaty. 

Adult 2, similar to the ¢ but duller in color throughout, and lacking the 
slight chestnut suffusion on crown and shoulders, and with the grayish tinge of 
cervix, upper back, and sides of head much less pronounced. 

Measurements. — Adult @, type, wing 193.5; tail 133; tarsus 26.8; exposed 
culmen 19. Adult 9, topotype, wing 192; tail 129; tarsus 26; exposed cul- 
men 18.6. 

The Green Pigeon differs in the islands as follows: S. permagnus is confined 
to the middle group of the Liu Kius, while S. medioximus is peculiar to the 
southern group; S. formose belongs further south still, to the island of 
Formosa. 

Stejneger’s type of S. permagnus is in the Museum at Tokyo, and I have not 
seen specimens of the species. In addition to the species here described being 
intermediate in size between S. permagnus and S. formose, it differs slightly in 
color from either of the two. In S. medioximus two sets of wing coverts are 
bordered with yellow, and the male has a decided wash of chestnut on both 
crown and shoulders. Stejneger especially describes his type as having only 
one set of coverts “the outer great coverts” edged with yellow. If the type of 
S. permagnus be a male, as was supposed, then the chestnut wash on the crown 
and shoulders of S. medioximus is a distinctive character, and yet again very 
different from the strong coloring of these parts in S. formose. 


Chalcophaps indica (Lixy.). 


Two specimens, ¢ and Q adults, from Ishigaki. The g§ taken March 20, 
the 9 taken June 10. [Many nests were found, containing two eggs each, 
usually placed in dead trees at from six to ten feet from the ground.] 

The two Ishigaki skins differ slightly from two Indian specimens of true 
C. indica with which I compared them. In the Liu Kiu birds the band on the 


aot 


BANGS: BIRDS FROM THE LIU KIU ISLANDS. 263 


lower back between the two gray bands is not coppery bronze, but is dull black, 
almost without metallic lustre, and the male hasa much greater amount of gray 
on back and upper neck. 

A green-winged dove was described by Swinhoe from Formosa as C. formo- 
sana, but is not recognized as distinct from @. indica by Count Salvadori, in 
the British Museum Catalogue (Vol. XXI. pp. 514-520). 


Megascops elegans (Cass1y). 


Two adults from Ishigaki, ¢ taken March 25, 9 March 23. Specimens 
were taken from March 1 to June 3. [Eggs, two in a clutch, were taken from 
holes in trees, seven to fifteen feet from the ground, from May 14 to June 27. ] 


Ninox japonica (Temm. & Scat.). 

Three specimens from Ishigaki, adult ¢ taken April 20, adult Q April 15, 
and a half-grown young, no date. These skins agree with Japanese specimens. 
The wing of the adult # measures 215, of the adult 2 210. 

Accipiter gularis (Temm. & Scut.). 

Three specimens, a 9(?) not in full adult plumage taken June 1, an adult 

&@ March 25, and a downy nestling June 27, all from Ishigaki. 
Butastur indicus (GMEt.). 


Two specimens from Ishigaki, neither in full plumage, the ¢ taken June 1, 
the Q March 23. 


Halcyon coromanda rufa (Wat.ace). 


Two specimens from Ishigaki, adult ¢ and 9, both taken April 25. Speci- 
mens were secured in Ishigaki and Taketomi from April 5 to June 10. [Eggs, 
three in a clutch, were collected from June 1 to June 21. The nests were in 
holes in trees at about ten feet from the ground.] I follow Dr. Stejneger in 
provisionally referring the Liu Kiu Ruddy Kingfisher to this form. 


Anthus maculatus Hones. 


One female taken in Ishigaki, April 7. 


Motacilla lugens Kittt. 


One adult ¢ in full spring plumage, taken in Ishigaki, June 1. This seems 
rather a late date for M. lugens to be in the Liu Kiu Islands. 


264 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


Hypsipetes pryeri Sreun. 


Five specimens from Ishigaki, an adult ¢ taken Feb. 29, an adult 9 April 
30, and three recently hatched young April 21. [Skins were also obtained in 
Kabama, and eggs, four in a clutch, were taken from April 2 to June 25.] 


Merula pallida (Gmet.). 


Two adults from Ishigaki, ¢ February 20, 9 May 1. (Many specimens 
were taken in Ishigaki up to June 20.) 


Merula chrysolaus (Trmm.). 


Two specimens from Ishigaki, adult ¢ May 7, adult 9 February 18. [Skins 
were collected in Ishigaki between February 18 and June 7.] 


Merula obscura (Gmet). 


Two adults from Ishigaki, @ February 22, 9 March 1. [Obtained in Ishi- 
gaki between February 20 and March 1.] 


Monticola solitaria (MUxt.). 


One adult 9, Ishigaki, March 23. 


Terpsiphone illex,! sp. nov. 


Tyee. — Mus. Comp. Zodl. No. 37,363. 


Two specimens from Ishigaki, anadult @ April 25, and an adult 9 May 31. 
[Specimens were taken between April 25 and June 20. Eggs, four in a clutch, 
between May 12 and June 13.] 

Characters. — Nearest to T. princeps (Temm.) of China and Japan, but 
smaller; rectrices narrower and squarer at ends ; wing shorter; primaries very 
short and decidedly narrower and more pointed at ends; wing formula differ- 
ent —4th primary longer than 5th (these two equal in 7. princeps, or 4th 
slightly shorter than 5th); feathers of crest in the @ all narrower, less 
rounded; colors much as in T. princeps, except less white in axillas and lining 
of wing; feathers of crest in the ¢ steel blue instead of purplish ; sides more 
heavily washed with brown. 

The 9 differs from the 9 of T. princeps in the same manner as does the @, 
z. €., it is smaller; in having narrower, shorter, more pointed primaries ; 
narrower rectrices ; crest feathers narrower and bluer, less purplish in color. 


1 Tllex, alluring, enticing. 


BANGS: BIRDS FROM THE LIU KIU ISLANDS. 265 


Color.—Adult @, head all round, throat, and jugulum blue black, rather more 
purplish on throat than on crown; back and scapulars glossy prune purple ; 
upper tail coverts and tail blue black ; wings black edged with purplish brown ; 
middle of belly and under tail coverts white; sides and flanks heavily washed 
with dark purplish brown; axillas dull brownish black with white tips ; under 
primary coverts black ; under wing coverts white streaked with pale brown. 

Female, crown blue black ; sides of head and cervix dark gray; throat dark 
gray becoming paler on jugulum; back chestnut, many of the feathers glossy 
purplish maroon at ends; tail dark purplish brown; wings hair brown edged 
with hazel, deeply so on secondaries and tertials ; middle of belly and under 
tail coverts white; sides and flanks washed with purplish brown; lining of 
wing as in the @, except primary coverts are hair brown instead of black. 

Measurements. — Adult @, type, wing 88; tail, to end of middle rectrices 
246.5, to end of longest other rectrices 113 ; greatest width of outer rectrix, 
8.8 ; tarsus 14.4 ; exposed culmen 15.4. 

Adult 9, topotype, No. 37,364, wing 82; tail 80; tarsus 14; exposed cul- 
men 15.4; width of outer rectrix 9.2. [In adult males of T. princeps the wing 
ranges from 92 to 94, and the greatest width of the outer rectrix is 11.4. In 
the adult females the wing measures from 88-90, and the greatest width of the 
outer rectrix is 12.] 

Remarks. — This appears to be the first record of a Paradise Flycatcher from 
the Liu Kiu Islands. Besides being considerably smaller than a T. princeps, it 
differs noticeably in its short, narrow, pointed primaries and narrow rectrices, 
and in having the 4th primary longer than the 5th. Like so many of the 
breeding birds of these islands, it is a well-marked island species. 


Zanthopygia owstoni,! sp. nov. 


Tyre. — Mus. Comp. Zodl., No. 37,367. 


One male from Ishigaki, June 20. 

Characters. — Nearest to Z. narcissina of Japan, but wing much shorter, 
due chiefly to the shortening of the primaries ; wing formula different —2nd 
primary shorter than 6th, 3rd about equal to 5th, 4th longest. In Z. narcissina 
the 2nd primary is much longer than 6th, 3rd equals 4th, these two longest and 
longer than 5th. In color the island bird is very different, the back is dark 
ereen, not black, the yellow frontal band extends all the way across base of 
culmen, the throat and breast are clear gamboge yellow, not orange. 

From Z. zanthopygia (Hay) the species can be distinguished by its yellow 
eyebrow (white in Z. zanthopygia) and differently marked wing. 

Color. — Male, apparently fully adult (9. unknown), narrow frontal band, 
extending directly across base of culmen and thence over eye to the supra- 
auricular region, gamboge yellow ; pileum, cheeks, back, and scapulars dusky 


1 Named in honor of Mr. Alan Owston. 


266 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


olive green ; rump bright gamboge yellow; upper tail coverts and tail black ; 
wings dark hair brown, the lesser coverts dull, dark plumbeous ; a large white 
wing patch, formed by the white color of the middle and most of the greater 
coverts; one or two (on each side) of the longer tertials narrowly edged with 
whitish for the basal half of the outer web ; throat, jugulum, and breast bright 
gamboge yellow, becoming yellowish white on belly and under tail coverts ; 
sides and flanks washed with olive green ; lining of wing and narrow inner 
margin of wing feathers, below, white. : 

Measurements. — Type @, wing 67 ; tail 45; tarsus 15.8; exposed culmen 
10.2; distance from tip of longest secondary to tip of longest primary about 15. 

Remarks.—In Proc. U. §. Nat. Mus., 1887, Vol. X, pp. 406-407. Stejneger 
pointed out the structural differences between the Liu Kiu species and Z. 
narcissina ; he, however, had but one young example of the island species, and 
on this account refrained from giving it a name. The one skin obtained by 
Zensaku bears out all the structural characters, and besides shows marked color 
differences from either Z. narcissina or Z. zanthopygia. 

The type of Z. owstoni, a male, appears to be in full breeding plumage, and 
if so, the dark olive green color of the back is unlike any other species, and 
would alone distinguish the Liu Kiu form. 


Cisticola brunniceps (Temm. & Scut.). 


Two adults from Ishigaki, ¢ taken March 7, 9 Junel. The fantail warbler 
is said to be the most abundant bird in the islands. [It builds its nest in 
grass a foot or two above the ground. Eggs, as many as seven in a clutch, were 
taken from March 25 to June 30.] 


Cettia cantillans (Temm. & Scut.). 


One adult 9 from Ishigaki, March 5. [Six specimens were taken on Ishigaki 
between March 5 and April 7.] 


Cettia cantans (Tem. & Scut.). 


Two specimens from Ishigaki, ¢ taken March 25, 9 April 6. [Specimens 
were secured between February 18 and April 6.] 


Hirundo rustica gutturalis (Scor.). 


Two adults from Ishigaki, ¢ April 4, 9 April 3, 1899. [Four birds in all 
were obtained on the island between April 2 and April 5.] 


Pericrocotus tegimae SrTesn. 


A pair of adults from Ishigaki, the 9 taken June 20, the ¢ June 10. These 
specimens agree exactly with Stejneger’s type. 


BANGS: BIRDS FROM THE LIU KIU ISLANDS. 267 


Lanius bucephalus Trmm. & Scat. 


One adult 9 from Ishigaki, May 10, 1899. I have compared this skin with 
an extensive series from Japan, and find it identical with mainland birds of 
the same sex in corresponding plumage. 


Parus stejnegeri,! sp. nov. 


Tyre. — Mus. Comp. Zoo6l., No. 87,392. 


Three specimens from Ishigaki, adult ¢ February 27, adult 9 June 1, and 
a nestling June 7. 

Characters. — Not nearly related to any known species ; general coloration 
gray-blue, black, and white ; under tail coverts mostly black; outer rectrices 
with no white, except a very narrow tip on the outer pair; no white patch on 
nape, a few feathers of this region with partly concealed white spots only 
noticeable when the feathers are disturbed ; general coloration of nestling 
greenish and dull yellow, showing the probable affinities of this species to some 
of the yellow and green titmice, such as P. jerdoni, P. inseparatus, ete., which 
have black under tail coverts and but little white in the tail. 

Color. — Adult g type,a large white auricular patch ; rest of head, throat, 
jugulum, and neck glossy blue-black ; a few feathers on middle of hind neck 
with small semi-concealed white spots; back, rump, and upper tail coverts 
dark plumbeous, slightly paler on lower rump; scapulars and broad edgings 
to greater and lesser wing coverts plumbeous ; some of the greater coverts 
tipped with drab-gray, forming a broken and inconspicuous wing bar; rest of 
wing grayish black, primaries edged with light plumbeous, secondaries with 
greenish gray, and tertials rather more broadly on outer webs with grayish 
white; primary coverts greenish gray ; a broad black stripe down middle of 
under parts, from jugulum to under tail coverts; sides and flanks dull olive 
gray, much paler and more drabby along edges of central black stripe and 
below the black of jugulum and sides of neck ; under tail coverts black, slightly 
edged and tipped with dark plumbeous, one or two of the shortest lateral ones 
a little marked with white ; rectrices, below blue-black, above, broadly edged 
on outer webs with dark plumbeous, the central pair mostly of this color, on 
both webs ; two outer rectrices with very narrow white tips, 2 mm. deep; 
bend of wing black; under primary coverts black tipped with white; axillas 
mostly white ; under sides of primaries grayish white on edges of inner webs. 

Adult 9, topotype, No. 37,393, similar in markings to the male, all the colors 
duller and lateral under tail coverts more noticeably marked with white. 

Nestling, topotype, about two-thirds grown, auricular patch olive yellow ; 
head, back, and throat dusky olive green, darkest on top of head and sides of 
throat ; a blackish line down middle of belly; sides, flanks, and under tail 


1 Named in honor of Dr. Leonhard Stejneger. 


268 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 


coverts dull olive yellow; wings grayish hair brown, scapulars and lesser 
coverts dull grayish olive, tips of greater coverts yellowish, forming a wing 
bar ; primaries and secondaries edged with greenish gray; tail grayish hair 
brown edged with greenish gray, outer rectrices barely tipped with whitish. 

Measurements. — Adult § type, wing 62; tail 55.5; tarsus 18.2; exposed 
culmen 11. Adult 9, topotype, No. 37,393, wing 60; tail 50; tarsus 18; 
exposed culmen 10.5. 


Corvus macrorhynchus levaillantii (Lzsson). 


Four specimens, all from Ishigaki, adult ¢ March 25, adult 9 March 28, and 
two young from the nest June 10. [Eggs, four in a clutch, were taken April 11 
to June 10.] 


Sturnia pyrrhogenys (Tem. & Scut.). . 


One male from Ishigaki, June 1, 1899. 


Zosterops loochooensis (Tristram). 


Two specimens from Ishigaki, adult ¢ March 18, adult 9 April 6. [Abun- 
dant on Ishigaki and Kuroshima. Skins were taken from February 18 to 
June 7, and eggs, four in a clutch, April 2 to June 25.] 

A careful comparison of these two specimens with numerous examples of 
Z. simplex and Z. japonica proves the Liu Kiu form to be a distinct island 
race, in spite of the doubts cast upon it in the latest review of the group.! 
But as no adequate description of it appears to have been published, I append 
the following : — 

Characters. —Nearest to Z. simplex of China, but bill heavier, wing longer ; 
of a brighter green color above, and brighter yellow color below; the species 
differs from Z. japonica in slightly shorter wing and in the color of the sides 
and flanks, which lack the strong vinous brown of this region in the Japanese 
species, and also in the primaries, being very short and narrow at tips (a char- 
acter presented by many of the species of birds peculiar to the Liu Kiu Islands) ; 
wing formula, Ist primary about equal to 6th, shorter than 5th, 2nd equal to 
4th, 3rd longest. 

Color. — Whole upper parts including margins of wing and tail feathers 
yellowish oil green, frontal region slightly yellower; wings and tail black 
(except for the green margins of the feathers); orbital ring silky white; a 
dusky spot below and in front of eye; chin and throat lemon yellow; breast 
and belly soiled whitish, faintly washed with yellowish along median line 
and with pale écru drab on sides and flanks; thighs yellowish white in front, 
dusky oil green behind ; under tail coverts lemon yellow ; bend of wing lemon 
yellow ; alula black ; lining of wing and axillas pale yellow ; narrow inner 
margins to wing feathers below whitish. 


1 Finsch, O. Zosteropidae. Das Tierreich, 1901, 15, p. 20. 


BANGS: BIRDS FROM THE LIU KIU ISLANDS. 269 


Measurements. — Adult ¢, No. 37,390, wing 57; tail 39.5 ; tarsus 18; ex- 


posed culmen 11.2; distance from tip of longest secondary to tip of longest 


primary 11. 
Adult 9, No. 37,391, wing 57; tail 40; tarsus 18; exposed culmen 11 ; 
distance from tip of longest secondary to tip of longest primary 11.5. 


Hmberiza spodocephala Patt. 


One male, not in full plumage, from Ishigaki, April 8. 


Passer montanus saturatus STE. 


One adult ¢ from Ishigaki, June 30. This specimen differs from the type 
of P. saturatus only by slightly paler colors, due to the more abraded condition 
of its plumage. [The bird was common in the island, and was breeding in the 
roofs of the houses. Eggs, seven in a clutch, were taken March 20 to June 25.] 


Coccothraustes coccothraustes japonicus (Trem. & Scut.). 


One female from Ishigaki, March 7. 


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* 


The following Publications of the Museum of Comparative Zodlogy 
are in preparation : — 


Reports on the Results of Dredging Operations in 1877, 1878, 1879, and 188), in charge of ALEX- 
ANDER AGASSIZ, by the U. S. Coast Survey Steamer “ Blake,” as follows: — 


E. EHLERS. The Annelids of the “ Blake.” 

CGC. HARTLAUB. The Comatula of the *‘ Blake,” with 15 Plates. 
H. LUDWIG. The Genus Pentacrinus. 

A. MILNE EDWARDS and E. L. BOUVIER. 
A. E. VERRILL. 


Reports on the Scientific Results of the Expedition to the Tropical Pacific, in charge of 
ALEXANDER AGASSIZ, on the U.S. Fish Commission Steamer ‘* Albatross,’’ from August, 
1899, to March, 1900, Commander Jefferson F. Moser, U. S. N., Commanding. 


The Crustacea of the ‘‘ Blake.”’ 
The Alcyonaria of the “ Blake.” 


Illustrations of North American MARINE INVERTEBRATES, from Drawings by Burk- 
HARDY, SONREL, and A. AGASSIZ, prepared under the direction of L. AGAss1z. 


LOUIS CABOT. Immature State of the Odonata, Part LV. 
E. L. MARK. Studies on Lepidosteus, continued. 
eS On Arachnactis. 
R. Tl. HILL. On the Geology of the Windward Islands. 
W. McM WOODWORTH. On the Bololo or Palolo of Fiji and Samoa. 
A. AGASSIZ and A. G. MAYER. The Acalephs of the East Coast of the United States. 
AGASSIZ and WHITMAN. Pelagic Fishes. Part II., with 14 Plates. 
J. C. BRANNER. ‘The Coral Reefs of Brazil. 


Reports on the Results of the Expedition of 1891 of the U. S. Fish Commission Steamer 
“ Albatross,’ Lieutenant Commander Z. L. TANNER, U.S. N., Commanding, in charge of 
ALEXANDER AGASSIZ, as follows: — 


A. AGASSIZ. The Pelagic Fauna. H. LUDWIG. The Starfishes. 
es The Echini. J. P. McMURRICH. The Actinarians. 
cs The Panamic Deep-Sea Fauna. 


FE. L. MARK. Branchiocerianthus. 


on serra rage pats JOHN MURRAY. The Bottom Specimens. 
The Thalassicole. <i 
CG. CHUN. ‘The Siphonophores. P. SCHIEMENZ. The Pteropods and Hete- 
hs ‘The Eyes of Deep-Sea Crustacea. ropods. . 
W. H. DALL. ‘The Mollusks. THEO. SYUDER. The Alcyonarians. 


M. P. A. TRAUSTEDT. 
Doliolide. 


H. J. HANSEN. $ ‘The Cirripeds. The Salpidz and 


W. A. HERDMAN. ‘The Ascidians. 


S. J. HICKSON. The Antipathids. 

W. E. HOYLE. The Cephalopods. ' 

G. VON KOCH. The Deep-Sea Corals. 

C. A. KOFOID. Solenogaster. 

R. VON LENDENFELD. ‘The Phospio- 
rescent Organs of Fishes. 


FE. P. VAN DUZEE. The Halobatide. 

H. B. WARD. The Sipunculids. 

H. V. WILSON. The Sponges. : 

W. MoM. WOODWORTH. The Nemerteans. 
U: The Annelids. 


PUBLICATIONS 


MUSEUM OF COMPARATIVE ZOOLOGY 


AT HARVARD COLLEGE. 


There have been published of the Butterins Vols. I. to XX XV. 5 
of the Memoirs, Vols. I. to XXIV. 

Vols. XXXVI., XXXVII., and XXXVIII. of the BuLLerin, 
and Vols. XXV., XXVI., and XXVII. of the Mremorrs, are now 
in course of pu GhoMiGH. 

The Butierin and Memoirs are devoted to the publication of 
original work by the Professors and Assistants of the Museum, of 
investigations carried on by students and others in the different 
Laboratories of Natural History, and of work by specialists based 
upon the Museum Collections and Explorations. 


The following publications are in preparation : — : 

Reports on the Results of Dredging Operations from 1877 to 1880, in charge of 
Alexander Agassiz, by the U. S. Ne: Survey Steamer ‘“ Blake,” Lieut. 
Commander C, D. Sigsbee, U. S. N., and Commander J. R. Bartlett, U.S. N., 
Commanding. 

Reports on the Results of the Expedition of 1891 of the U.S. Fish Commission 
Steamer “ Albatross,” Lieut. Commander Z. L. Tanner, U. 8. N., Com- 
manding, in charge of Alexander Agassiz. 

Reports on the Scientific Results of the Expedition to the Tropical Pacifie, in 
charge of Alexander Agassiz, on the U.S. Fish Commission Steamer 
“ Albatross,” from August, 1899, to March, 1900, Commander Jefferson F. 
Moser, U.S. N., Commanding. 

Contributions from the Zodlogical Laboratory, Professor B. l.. Mark, Director. 

Contributions from the Geological Laboratory, in charge of Professor N. S. 
Shaler. 


These publications are issued in numbers at irregular inter- 
vals; one volume of the Bulletin (8vo) and half a volume of the 
Memoirs (4to) usually appear annually. Each number of the Bul- 
letin and of the Memoirs is also sold separately. A price list 
of the publications of the Museum will be sent on application 
to the Librarian of the Museum of Comparative Zodlogy, Cam- 
bridge, Mass. 


ie : . | | 


DATE DUE 


DEMCO, INC. 38-2931 


ACE 
#OOKRINDING CO. ING. 


AUG 23 1984 


200 CAMBRIDGE STREET 
CHARLESTOWN, MASS. 


3 2044 066 303 355 


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